biorousso - Contributions [fr]

WEIT 2012 Chap1

2012-05-04T14:22:42Z

MorganeV : /* References */

<big>'''WHAT IS EVOLUTION'''</big> 
=What is the definition of Evolution?=

Evolution is a gradual process in which the biological populations change into a different and usually more complex or better form.
Life on Earth began with a universal common ancestor. It changed gradually, taking several millions of years.
This universal common ancestor, named LUCA (Last Universal Common Ancestor), branched out over time, throwing off many new and diverse species. This mechanism of evolutionary change is called natural selection. When you break that statement down, you find that it really consists of six components.

=What are the six components of the statement of evolution?=

The six components are

1. Evolution

2. Gradualism

3. Speciation

4. Common ancestry

5. Natural selection

6. Nonselective mechanisms of evolutionary change

Let see each of these components closer.

==What is Evolution?==
Evolution is the fact that a population of organisms undergoes genetic change over time. Individual organisms do not evolve.
The differences are based on the changes into the DNA, which originate as mutations. All the populations evolve but not at the same rate.
The theory of evolution doesn't predict that population will constantly be evolving, or how fast they will change when they do. It depends on the evolutionary pressures they experience.

*'''See Appendix 1'''

==What is Gradualism?==
''Gradualism'' is the fact that it takes many generations to produce a substantial evolutionary change. The evolution of new features can take over hundreds or thousands (even millions) of generations. A species evolve faster or slower as evolutionary pressures wax and wane. Also, when the natural selection is strong, evolutionary change can be fast. But once a species becomes well adapted to a stable habitat, evolution often slows down.
Many living species share fundamental traits such as biochemical pathways that we use to produce energy, our standard four letters DNA code, and how that code is read and translated into proteins. This tells us that every species goes back to a single common ancestor (who had those traits and passed them on to its descendants).

Gradualism being evolutionary changes over time, it's often represented as a tree whose roots would be the common ancestor of all the species it represents. The difference between a gradualism and a punctuated equilibrium representation is that a punctuated equilibrium representation illustrates the evolutionary changes at given time and that gradualism one tries to show all the phases a species went through. In Appendix 4, there's a comparison of the two representations.

*'''See Appendix 2'''

==What is Speciation?==
''Speciation'', also called ''splitting'', is a very slow process which explains how a single ancestral species can split in several descendant species. More precisely, it's the appearance of slight differences between two different populations of the same species and we consider that the splitting really occurred when the differences become so important that the two populations can no longer interbreed. Species themselves cannot split and don't have to. This process doesn't happen quite often, but enough to explain us the great diversity of the terrestrial flora and fauna.
Since it doubles the number of opportunities for future speciation for a species, speciation might increase exponentially the number of species, but more than 99 percent of the species did actually extinct without leaving any descendant.

One of the most interesting examples brings us millions years ago around the Triassic period and explains us the link between birds and reptiles or how a bipedal dinosaur, let’s call him ancestor X, split in order to give two new kinds of dinosaurs, one having actual reptiles’ features and producing bipedal, carnivorous dinosaurs, like the T.rex, and the other producing all the birds. This splitting would at first only be noticed by slight differences, like two populations of the same species. We’ll have to wait thousands generations to see the dinosaur kind producing bird start flying.

This process is studied in a more detailed way in ch.7: "The Origin of Species".

==What is Common ancestry?==
Common ancestry is the flip side of speciation. We can always look back in time, using either DNA sequences or fossils, and find descendants joining at their ancestors.
Every pair of species shares a common ancestor sometimes in the past.
To express the evolutionary relatedness among species through time, we use The Tree of Life. This Tree illustration has been first proposed by Darwin in the 19th century. This Tree of Life could be done by looking at physical traits. Now we have the ability to make a Tree of Life even more precise with the knowing of DNA.

Appendix 3, Picture A, represents Charles Darwin’s first diagram of an evolutionary tree from his “First Notebook on Transmutation of Species” (1837) is on view at the American Museum of Natural History in New York City.
It stands to reason that if the history of life forms a tree, with all species originating from a single trunk, then one can find a common origin for every existing species by tracing each twig (=existing species) back through its branches until they intersect at the branch they have in common. This node as we have seen is their common ancestor.
On Appendix 3, Picture B, we can see an example of an evolutionary Tree on which we can clearly see that each branch intercept a single common ancestor.

*'''See Appendix 3'''

==What is Natural selection?==
Natural selection is a process which requires that individuals of a species vary genetically in their ability to survive and reproduce in their environment.
In a more detailed way, if individuals within a species differ genetically from one another, and some of those differences affect the abilities of an individual to survive and reproduce in its environment, then in the next generation the “good” genes that lead to a higher survival and reproduction level will have relatively more copies than the “not so good” genes. Over time, the population will gradually become more and more suited to its environment as helpful mutations arise and spread through the population, while deleterious ones are weeded out. Ultimately, this process produces organisms that are well adapted to their habitats and way of life.

Let illustrate this process by a simple example. The woolly mammoth inhabited the northern parts Eurasia and North America, places were the weather can be especially cold. He was adapted to those extreme temperatures by bearing a thick coat of hair.
It probably descended from mammoth ancestors that had little hair. Mutations in the ancestral species led to some individuals being hairier than others. When the climate became cold the shaggy individuals were better able to tolerate their frigid surroundings and thus left more offspring than their balder fellows. By the way, the next generations will have a hairier average mammoth. Let this process continue over some thousands of generations and the smooth mammoth will be replaced by a shaggy one.
In Appendix 5, there is an illustration comparing a woolly mammoth and a modern elephant. A clear difference can be observed concerning the thickness of the hair of the mammoth especially on his ventral side.

Another example: Lamarck believed that giraffe's were no bigger than horses, but as there was little food around other than that on high up branches, a giraffe managed to stretch its neck and make it longer to reach the branches. When it mated, its offspring also had long necks. Ultimately, this process will continue through generations until our modern giraffe.
*'''see Appendix 4'''

==What are the Nonselective mechanisms of evolutionary change?==
These mechanisms, also called ''genetic drift'', have nothing to do with adaptation; it is more about the random changes in the proportion of alleles due to the sampling effects of reproduction. Because natural selection is the only process that generates adaptation, the influence of the nonselective mechanisms of evolutionary change is less. This also helps us explain some neutral (nor useful or injurious) and non-adaptive features, like some DNA variations, even if we cannot prove that these features have absolutely no selective advantages. It can only play an evolutionary role on small population, and, because it has nothing to do with adaptation, it might sometimes just preserve bad alleles instead of destroying them, for example the high rate of genetically based diseases in small, isolated human communities, like Gaucher’s disease in northern Swedes.

=Can we consider Evolution as a theory?=
First of all, we have to make clear what a theory is: "A theory is a coherent group of tested general propositions, ''commonly regarded as correct'', that can be used as principles of explanation and prediction for a class of phenomena."
So in science, a theory is much more than only a supposition about how things are: it is a well-thought-out group of propositions meant to explain facts about the real world.

*'''see Appendix 5'''

=References=
*http://dictionary.reference.com/browse/theory
*http://en.wikipedia.org/wiki/Bipedalism

----
*retour à [[Evolution_3BIbDF10-11_2011/12]] 
*retour à [[Accueil]]

WEIT 2012 Chap1

2012-05-04T14:18:08Z

MorganeV : /* What is Gradualism? */

<big>'''WHAT IS EVOLUTION'''</big> 
=What is the definition of Evolution?=

Evolution is a gradual process in which the biological populations change into a different and usually more complex or better form.
Life on Earth began with a universal common ancestor. It changed gradually, taking several millions of years.
This universal common ancestor, named LUCA (Last Universal Common Ancestor), branched out over time, throwing off many new and diverse species. This mechanism of evolutionary change is called natural selection. When you break that statement down, you find that it really consists of six components.

=What are the six components of the statement of evolution?=

The six components are

1. Evolution

2. Gradualism

3. Speciation

4. Common ancestry

5. Natural selection

6. Nonselective mechanisms of evolutionary change

Let see each of these components closer.

==What is Evolution?==
Evolution is the fact that a population of organisms undergoes genetic change over time. Individual organisms do not evolve.
The differences are based on the changes into the DNA, which originate as mutations. All the populations evolve but not at the same rate.
The theory of evolution doesn't predict that population will constantly be evolving, or how fast they will change when they do. It depends on the evolutionary pressures they experience.

*'''See Appendix 1'''

==What is Gradualism?==
''Gradualism'' is the fact that it takes many generations to produce a substantial evolutionary change. The evolution of new features can take over hundreds or thousands (even millions) of generations. A species evolve faster or slower as evolutionary pressures wax and wane. Also, when the natural selection is strong, evolutionary change can be fast. But once a species becomes well adapted to a stable habitat, evolution often slows down.
Many living species share fundamental traits such as biochemical pathways that we use to produce energy, our standard four letters DNA code, and how that code is read and translated into proteins. This tells us that every species goes back to a single common ancestor (who had those traits and passed them on to its descendants).

Gradualism being evolutionary changes over time, it's often represented as a tree whose roots would be the common ancestor of all the species it represents. The difference between a gradualism and a punctuated equilibrium representation is that a punctuated equilibrium representation illustrates the evolutionary changes at given time and that gradualism one tries to show all the phases a species went through. In Appendix 4, there's a comparison of the two representations.

*'''See Appendix 2'''

==What is Speciation?==
''Speciation'', also called ''splitting'', is a very slow process which explains how a single ancestral species can split in several descendant species. More precisely, it's the appearance of slight differences between two different populations of the same species and we consider that the splitting really occurred when the differences become so important that the two populations can no longer interbreed. Species themselves cannot split and don't have to. This process doesn't happen quite often, but enough to explain us the great diversity of the terrestrial flora and fauna.
Since it doubles the number of opportunities for future speciation for a species, speciation might increase exponentially the number of species, but more than 99 percent of the species did actually extinct without leaving any descendant.

One of the most interesting examples brings us millions years ago around the Triassic period and explains us the link between birds and reptiles or how a bipedal dinosaur, let’s call him ancestor X, split in order to give two new kinds of dinosaurs, one having actual reptiles’ features and producing bipedal, carnivorous dinosaurs, like the T.rex, and the other producing all the birds. This splitting would at first only be noticed by slight differences, like two populations of the same species. We’ll have to wait thousands generations to see the dinosaur kind producing bird start flying.

This process is studied in a more detailed way in ch.7: "The Origin of Species".

==What is Common ancestry?==
Common ancestry is the flip side of speciation. We can always look back in time, using either DNA sequences or fossils, and find descendants joining at their ancestors.
Every pair of species shares a common ancestor sometimes in the past.
To express the evolutionary relatedness among species through time, we use The Tree of Life. This Tree illustration has been first proposed by Darwin in the 19th century. This Tree of Life could be done by looking at physical traits. Now we have the ability to make a Tree of Life even more precise with the knowing of DNA.

Appendix 3, Picture A, represents Charles Darwin’s first diagram of an evolutionary tree from his “First Notebook on Transmutation of Species” (1837) is on view at the American Museum of Natural History in New York City.
It stands to reason that if the history of life forms a tree, with all species originating from a single trunk, then one can find a common origin for every existing species by tracing each twig (=existing species) back through its branches until they intersect at the branch they have in common. This node as we have seen is their common ancestor.
On Appendix 3, Picture B, we can see an example of an evolutionary Tree on which we can clearly see that each branch intercept a single common ancestor.

*'''See Appendix 3'''

==What is Natural selection?==
Natural selection is a process which requires that individuals of a species vary genetically in their ability to survive and reproduce in their environment.
In a more detailed way, if individuals within a species differ genetically from one another, and some of those differences affect the abilities of an individual to survive and reproduce in its environment, then in the next generation the “good” genes that lead to a higher survival and reproduction level will have relatively more copies than the “not so good” genes. Over time, the population will gradually become more and more suited to its environment as helpful mutations arise and spread through the population, while deleterious ones are weeded out. Ultimately, this process produces organisms that are well adapted to their habitats and way of life.

Let illustrate this process by a simple example. The woolly mammoth inhabited the northern parts Eurasia and North America, places were the weather can be especially cold. He was adapted to those extreme temperatures by bearing a thick coat of hair.
It probably descended from mammoth ancestors that had little hair. Mutations in the ancestral species led to some individuals being hairier than others. When the climate became cold the shaggy individuals were better able to tolerate their frigid surroundings and thus left more offspring than their balder fellows. By the way, the next generations will have a hairier average mammoth. Let this process continue over some thousands of generations and the smooth mammoth will be replaced by a shaggy one.
In Appendix 5, there is an illustration comparing a woolly mammoth and a modern elephant. A clear difference can be observed concerning the thickness of the hair of the mammoth especially on his ventral side.

Another example: Lamarck believed that giraffe's were no bigger than horses, but as there was little food around other than that on high up branches, a giraffe managed to stretch its neck and make it longer to reach the branches. When it mated, its offspring also had long necks. Ultimately, this process will continue through generations until our modern giraffe.
*'''see Appendix 4'''

==What are the Nonselective mechanisms of evolutionary change?==
These mechanisms, also called ''genetic drift'', have nothing to do with adaptation; it is more about the random changes in the proportion of alleles due to the sampling effects of reproduction. Because natural selection is the only process that generates adaptation, the influence of the nonselective mechanisms of evolutionary change is less. This also helps us explain some neutral (nor useful or injurious) and non-adaptive features, like some DNA variations, even if we cannot prove that these features have absolutely no selective advantages. It can only play an evolutionary role on small population, and, because it has nothing to do with adaptation, it might sometimes just preserve bad alleles instead of destroying them, for example the high rate of genetically based diseases in small, isolated human communities, like Gaucher’s disease in northern Swedes.

=Can we consider Evolution as a theory?=
First of all, we have to make clear what a theory is: "A theory is a coherent group of tested general propositions, ''commonly regarded as correct'', that can be used as principles of explanation and prediction for a class of phenomena."
So in science, a theory is much more than only a supposition about how things are: it is a well-thought-out group of propositions meant to explain facts about the real world.

*'''see Appendix 5'''

=References=
*http://dictionary.reference.com/browse/theory
*http://en.wikipedia.org/wiki/Bipedalism

{{co|don't you think that you could bring some examples to illustrate this chapter which is a summary of the main points discussed in the book. The other option that would be even better would be to make LINKS with the other chapters (the other wiki pages)...}}--[[Utilisateur:Pierre.brawand|Pierre.brawand]] 30 mars 2012 à 10:57 (CEST)
{{co|Examples?}}--[[Utilisateur:Pierre.brawand|Pierre.brawand]] 25 avril 2012 à 18:28 (CEST)
----
*retour à [[Evolution_3BIbDF10-11_2011/12]] 
*retour à [[Accueil]]

WEIT 2012 Chap1

2012-05-04T14:12:19Z

MorganeV : /* What is Common ancestry? */

<big>'''WHAT IS EVOLUTION'''</big> 
=What is the definition of Evolution?=

Evolution is a gradual process in which the biological populations change into a different and usually more complex or better form.
Life on Earth began with a universal common ancestor. It changed gradually, taking several millions of years.
This universal common ancestor, named LUCA (Last Universal Common Ancestor), branched out over time, throwing off many new and diverse species. This mechanism of evolutionary change is called natural selection. When you break that statement down, you find that it really consists of six components.

=What are the six components of the statement of evolution?=

The six components are

1. Evolution

2. Gradualism

3. Speciation

4. Common ancestry

5. Natural selection

6. Nonselective mechanisms of evolutionary change

Let see each of these components closer.

==What is Evolution?==
Evolution is the fact that a population of organisms undergoes genetic change over time. Individual organisms do not evolve.
The differences are based on the changes into the DNA, which originate as mutations. All the populations evolve but not at the same rate.
The theory of evolution doesn't predict that population will constantly be evolving, or how fast they will change when they do. It depends on the evolutionary pressures they experience.

*'''See Appendix 1'''

==What is Gradualism?==
''Gradualism'' is the fact that it takes many generations to produce a substantial evolutionary change. The evolution of new features can take over hundreds or thousands (even millions) of generations. A species evolve faster or slower as evolutionary pressures wax and wane. Also, when the natural selection is strong, evolutionary change can be fast. But once a species becomes well adapted to a stable habitat, evolution often slows down.
Many living species share fundamental traits such as biochemical pathways that we use to produce energy, our standard four letters DNA code, and how that code is read and translated into proteins. This tells us that every species goes back to a single common ancestor (who had those traits and passed them on to its descendants).

Gradualism being evolutionary changes over time, it's often represented as a tree whose roots would be the common ancestor of all the species it represents. The difference between a gradualism and a punctuated equilibrium representation is that a punctuated equilibrium representation illustrates the evolutionary changes at given time and that gradualism one tries to show all the phases a species went through. In Appendix 4, there's a comparison of the two representations.

*'''See Appendix 2'''

==What is Speciation?==
''Speciation'', also called ''splitting'', is a very slow process which explains how a single ancestral species can split in several descendant species. More precisely, it's the appearance of slight differences between two different populations of the same species and we consider that the splitting really occurred when the differences become so important that the two populations can no longer interbreed. Species themselves cannot split and don't have to. This process doesn't happen quite often, but enough to explain us the great diversity of the terrestrial flora and fauna.
Since it doubles the number of opportunities for future speciation for a species, speciation might increase exponentially the number of species, but more than 99 percent of the species did actually extinct without leaving any descendant.

One of the most interesting examples brings us millions years ago around the Triassic period and explains us the link between birds and reptiles or how a bipedal dinosaur, let’s call him ancestor X, split in order to give two new kinds of dinosaurs, one having actual reptiles’ features and producing bipedal, carnivorous dinosaurs, like the T.rex, and the other producing all the birds. This splitting would at first only be noticed by slight differences, like two populations of the same species. We’ll have to wait thousands generations to see the dinosaur kind producing bird start flying.

This process is studied in a more detailed way in ch.7: "The Origin of Species".

==What is Common ancestry?==
Common ancestry is the flip side of speciation. We can always look back in time, using either DNA sequences or fossils, and find descendants joining at their ancestors.
Every pair of species shares a common ancestor sometimes in the past.
To express the evolutionary relatedness among species through time, we use The Tree of Life. This Tree illustration has been first proposed by Darwin in the 19th century. This Tree of Life could be done by looking at physical traits. Now we have the ability to make a Tree of Life even more precise with the knowing of DNA.

Appendix 3, Picture A, represents Charles Darwin’s first diagram of an evolutionary tree from his “First Notebook on Transmutation of Species” (1837) is on view at the American Museum of Natural History in New York City.
It stands to reason that if the history of life forms a tree, with all species originating from a single trunk, then one can find a common origin for every existing species by tracing each twig (=existing species) back through its branches until they intersect at the branch they have in common. This node as we have seen is their common ancestor.
On Appendix 3, Picture B, we can see an example of an evolutionary Tree on which we can clearly see that each branch intercept a single common ancestor.

*'''See Appendix 3'''

==What is Natural selection?==
Natural selection is a process which requires that individuals of a species vary genetically in their ability to survive and reproduce in their environment.
In a more detailed way, if individuals within a species differ genetically from one another, and some of those differences affect the abilities of an individual to survive and reproduce in its environment, then in the next generation the “good” genes that lead to a higher survival and reproduction level will have relatively more copies than the “not so good” genes. Over time, the population will gradually become more and more suited to its environment as helpful mutations arise and spread through the population, while deleterious ones are weeded out. Ultimately, this process produces organisms that are well adapted to their habitats and way of life.

Let illustrate this process by a simple example. The woolly mammoth inhabited the northern parts Eurasia and North America, places were the weather can be especially cold. He was adapted to those extreme temperatures by bearing a thick coat of hair.
It probably descended from mammoth ancestors that had little hair. Mutations in the ancestral species led to some individuals being hairier than others. When the climate became cold the shaggy individuals were better able to tolerate their frigid surroundings and thus left more offspring than their balder fellows. By the way, the next generations will have a hairier average mammoth. Let this process continue over some thousands of generations and the smooth mammoth will be replaced by a shaggy one.
In Appendix 5, there is an illustration comparing a woolly mammoth and a modern elephant. A clear difference can be observed concerning the thickness of the hair of the mammoth especially on his ventral side.

Another example: Lamarck believed that giraffe's were no bigger than horses, but as there was little food around other than that on high up branches, a giraffe managed to stretch its neck and make it longer to reach the branches. When it mated, its offspring also had long necks. Ultimately, this process will continue through generations until our modern giraffe.
*'''see Appendix 4'''

==What are the Nonselective mechanisms of evolutionary change?==
These mechanisms, also called ''genetic drift'', have nothing to do with adaptation; it is more about the random changes in the proportion of alleles due to the sampling effects of reproduction. Because natural selection is the only process that generates adaptation, the influence of the nonselective mechanisms of evolutionary change is less. This also helps us explain some neutral (nor useful or injurious) and non-adaptive features, like some DNA variations, even if we cannot prove that these features have absolutely no selective advantages. It can only play an evolutionary role on small population, and, because it has nothing to do with adaptation, it might sometimes just preserve bad alleles instead of destroying them, for example the high rate of genetically based diseases in small, isolated human communities, like Gaucher’s disease in northern Swedes.

=Can we consider Evolution as a theory?=
First of all, we have to make clear what a theory is: "A theory is a coherent group of tested general propositions, ''commonly regarded as correct'', that can be used as principles of explanation and prediction for a class of phenomena."
So in science, a theory is much more than only a supposition about how things are: it is a well-thought-out group of propositions meant to explain facts about the real world.

*'''see Appendix 5'''

=References=
*http://dictionary.reference.com/browse/theory
*http://en.wikipedia.org/wiki/Bipedalism

{{co|don't you think that you could bring some examples to illustrate this chapter which is a summary of the main points discussed in the book. The other option that would be even better would be to make LINKS with the other chapters (the other wiki pages)...}}--[[Utilisateur:Pierre.brawand|Pierre.brawand]] 30 mars 2012 à 10:57 (CEST)
{{co|Examples?}}--[[Utilisateur:Pierre.brawand|Pierre.brawand]] 25 avril 2012 à 18:28 (CEST)
----
*retour à [[Evolution_3BIbDF10-11_2011/12]] 
*retour à [[Accueil]]

WEIT 2012 Chap1

2012-05-04T14:11:56Z

MorganeV : /* What is Natural selection? */

<big>'''WHAT IS EVOLUTION'''</big> 
=What is the definition of Evolution?=

Evolution is a gradual process in which the biological populations change into a different and usually more complex or better form.
Life on Earth began with a universal common ancestor. It changed gradually, taking several millions of years.
This universal common ancestor, named LUCA (Last Universal Common Ancestor), branched out over time, throwing off many new and diverse species. This mechanism of evolutionary change is called natural selection. When you break that statement down, you find that it really consists of six components.

=What are the six components of the statement of evolution?=

The six components are

1. Evolution

2. Gradualism

3. Speciation

4. Common ancestry

5. Natural selection

6. Nonselective mechanisms of evolutionary change

Let see each of these components closer.

==What is Evolution?==
Evolution is the fact that a population of organisms undergoes genetic change over time. Individual organisms do not evolve.
The differences are based on the changes into the DNA, which originate as mutations. All the populations evolve but not at the same rate.
The theory of evolution doesn't predict that population will constantly be evolving, or how fast they will change when they do. It depends on the evolutionary pressures they experience.

*'''See Appendix 1'''

==What is Gradualism?==
''Gradualism'' is the fact that it takes many generations to produce a substantial evolutionary change. The evolution of new features can take over hundreds or thousands (even millions) of generations. A species evolve faster or slower as evolutionary pressures wax and wane. Also, when the natural selection is strong, evolutionary change can be fast. But once a species becomes well adapted to a stable habitat, evolution often slows down.
Many living species share fundamental traits such as biochemical pathways that we use to produce energy, our standard four letters DNA code, and how that code is read and translated into proteins. This tells us that every species goes back to a single common ancestor (who had those traits and passed them on to its descendants).

Gradualism being evolutionary changes over time, it's often represented as a tree whose roots would be the common ancestor of all the species it represents. The difference between a gradualism and a punctuated equilibrium representation is that a punctuated equilibrium representation illustrates the evolutionary changes at given time and that gradualism one tries to show all the phases a species went through. In Appendix 4, there's a comparison of the two representations.

*'''See Appendix 2'''

==What is Speciation?==
''Speciation'', also called ''splitting'', is a very slow process which explains how a single ancestral species can split in several descendant species. More precisely, it's the appearance of slight differences between two different populations of the same species and we consider that the splitting really occurred when the differences become so important that the two populations can no longer interbreed. Species themselves cannot split and don't have to. This process doesn't happen quite often, but enough to explain us the great diversity of the terrestrial flora and fauna.
Since it doubles the number of opportunities for future speciation for a species, speciation might increase exponentially the number of species, but more than 99 percent of the species did actually extinct without leaving any descendant.

One of the most interesting examples brings us millions years ago around the Triassic period and explains us the link between birds and reptiles or how a bipedal dinosaur, let’s call him ancestor X, split in order to give two new kinds of dinosaurs, one having actual reptiles’ features and producing bipedal, carnivorous dinosaurs, like the T.rex, and the other producing all the birds. This splitting would at first only be noticed by slight differences, like two populations of the same species. We’ll have to wait thousands generations to see the dinosaur kind producing bird start flying.

This process is studied in a more detailed way in ch.7: "The Origin of Species".

==What is Common ancestry?==
Common ancestry is the flip side of speciation. We can always look back in time, using either DNA sequences or fossils, and find descendants joining at their ancestors.
Every pair of species shares a common ancestor sometimes in the past.
To express the evolutionary relatedness among species through time, we use The Tree of Life. This Tree illustration has been first proposed by Darwin in the 19th century. This Tree of Life could be done by looking at physical traits. Now we have the ability to make a Tree of Life even more precise with the knowing of DNA.

Appendix 3, Picture A, represents Charles Darwin’s first diagram of an evolutionary tree from his “First Notebook on Transmutation of Species” (1837) is on view at the American Museum of Natural History in New York City.
It stands to reason that if the history of life forms a tree, with all species originating from a single trunk, then one can find a common origin for every existing species by tracing each twig (=existing species) back through its branches until they intersect at the branch they have in common. This node as we have seen is their common ancestor.
On Appendix 3, Picture B, we can see an example of an evolutionary Tree on which we can clearly see that each branch intercept a single common ancestor.

EXAMPLE

*'''See Appendix 3'''

==What is Natural selection?==
Natural selection is a process which requires that individuals of a species vary genetically in their ability to survive and reproduce in their environment.
In a more detailed way, if individuals within a species differ genetically from one another, and some of those differences affect the abilities of an individual to survive and reproduce in its environment, then in the next generation the “good” genes that lead to a higher survival and reproduction level will have relatively more copies than the “not so good” genes. Over time, the population will gradually become more and more suited to its environment as helpful mutations arise and spread through the population, while deleterious ones are weeded out. Ultimately, this process produces organisms that are well adapted to their habitats and way of life.

Let illustrate this process by a simple example. The woolly mammoth inhabited the northern parts Eurasia and North America, places were the weather can be especially cold. He was adapted to those extreme temperatures by bearing a thick coat of hair.
It probably descended from mammoth ancestors that had little hair. Mutations in the ancestral species led to some individuals being hairier than others. When the climate became cold the shaggy individuals were better able to tolerate their frigid surroundings and thus left more offspring than their balder fellows. By the way, the next generations will have a hairier average mammoth. Let this process continue over some thousands of generations and the smooth mammoth will be replaced by a shaggy one.
In Appendix 5, there is an illustration comparing a woolly mammoth and a modern elephant. A clear difference can be observed concerning the thickness of the hair of the mammoth especially on his ventral side.

Another example: Lamarck believed that giraffe's were no bigger than horses, but as there was little food around other than that on high up branches, a giraffe managed to stretch its neck and make it longer to reach the branches. When it mated, its offspring also had long necks. Ultimately, this process will continue through generations until our modern giraffe.
*'''see Appendix 4'''

==What are the Nonselective mechanisms of evolutionary change?==
These mechanisms, also called ''genetic drift'', have nothing to do with adaptation; it is more about the random changes in the proportion of alleles due to the sampling effects of reproduction. Because natural selection is the only process that generates adaptation, the influence of the nonselective mechanisms of evolutionary change is less. This also helps us explain some neutral (nor useful or injurious) and non-adaptive features, like some DNA variations, even if we cannot prove that these features have absolutely no selective advantages. It can only play an evolutionary role on small population, and, because it has nothing to do with adaptation, it might sometimes just preserve bad alleles instead of destroying them, for example the high rate of genetically based diseases in small, isolated human communities, like Gaucher’s disease in northern Swedes.

=Can we consider Evolution as a theory?=
First of all, we have to make clear what a theory is: "A theory is a coherent group of tested general propositions, ''commonly regarded as correct'', that can be used as principles of explanation and prediction for a class of phenomena."
So in science, a theory is much more than only a supposition about how things are: it is a well-thought-out group of propositions meant to explain facts about the real world.

*'''see Appendix 5'''

=References=
*http://dictionary.reference.com/browse/theory
*http://en.wikipedia.org/wiki/Bipedalism

{{co|don't you think that you could bring some examples to illustrate this chapter which is a summary of the main points discussed in the book. The other option that would be even better would be to make LINKS with the other chapters (the other wiki pages)...}}--[[Utilisateur:Pierre.brawand|Pierre.brawand]] 30 mars 2012 à 10:57 (CEST)
{{co|Examples?}}--[[Utilisateur:Pierre.brawand|Pierre.brawand]] 25 avril 2012 à 18:28 (CEST)
----
*retour à [[Evolution_3BIbDF10-11_2011/12]] 
*retour à [[Accueil]]

WEIT 2012 Chap1

2012-05-04T14:11:38Z

MorganeV : /* Can we consider Evolution as a theory? */

<big>'''WHAT IS EVOLUTION'''</big> 
=What is the definition of Evolution?=

Evolution is a gradual process in which the biological populations change into a different and usually more complex or better form.
Life on Earth began with a universal common ancestor. It changed gradually, taking several millions of years.
This universal common ancestor, named LUCA (Last Universal Common Ancestor), branched out over time, throwing off many new and diverse species. This mechanism of evolutionary change is called natural selection. When you break that statement down, you find that it really consists of six components.

=What are the six components of the statement of evolution?=

The six components are

1. Evolution

2. Gradualism

3. Speciation

4. Common ancestry

5. Natural selection

6. Nonselective mechanisms of evolutionary change

Let see each of these components closer.

==What is Evolution?==
Evolution is the fact that a population of organisms undergoes genetic change over time. Individual organisms do not evolve.
The differences are based on the changes into the DNA, which originate as mutations. All the populations evolve but not at the same rate.
The theory of evolution doesn't predict that population will constantly be evolving, or how fast they will change when they do. It depends on the evolutionary pressures they experience.

*'''See Appendix 1'''

==What is Gradualism?==
''Gradualism'' is the fact that it takes many generations to produce a substantial evolutionary change. The evolution of new features can take over hundreds or thousands (even millions) of generations. A species evolve faster or slower as evolutionary pressures wax and wane. Also, when the natural selection is strong, evolutionary change can be fast. But once a species becomes well adapted to a stable habitat, evolution often slows down.
Many living species share fundamental traits such as biochemical pathways that we use to produce energy, our standard four letters DNA code, and how that code is read and translated into proteins. This tells us that every species goes back to a single common ancestor (who had those traits and passed them on to its descendants).

Gradualism being evolutionary changes over time, it's often represented as a tree whose roots would be the common ancestor of all the species it represents. The difference between a gradualism and a punctuated equilibrium representation is that a punctuated equilibrium representation illustrates the evolutionary changes at given time and that gradualism one tries to show all the phases a species went through. In Appendix 4, there's a comparison of the two representations.

*'''See Appendix 2'''

==What is Speciation?==
''Speciation'', also called ''splitting'', is a very slow process which explains how a single ancestral species can split in several descendant species. More precisely, it's the appearance of slight differences between two different populations of the same species and we consider that the splitting really occurred when the differences become so important that the two populations can no longer interbreed. Species themselves cannot split and don't have to. This process doesn't happen quite often, but enough to explain us the great diversity of the terrestrial flora and fauna.
Since it doubles the number of opportunities for future speciation for a species, speciation might increase exponentially the number of species, but more than 99 percent of the species did actually extinct without leaving any descendant.

One of the most interesting examples brings us millions years ago around the Triassic period and explains us the link between birds and reptiles or how a bipedal dinosaur, let’s call him ancestor X, split in order to give two new kinds of dinosaurs, one having actual reptiles’ features and producing bipedal, carnivorous dinosaurs, like the T.rex, and the other producing all the birds. This splitting would at first only be noticed by slight differences, like two populations of the same species. We’ll have to wait thousands generations to see the dinosaur kind producing bird start flying.

This process is studied in a more detailed way in ch.7: "The Origin of Species".

==What is Common ancestry?==
Common ancestry is the flip side of speciation. We can always look back in time, using either DNA sequences or fossils, and find descendants joining at their ancestors.
Every pair of species shares a common ancestor sometimes in the past.
To express the evolutionary relatedness among species through time, we use The Tree of Life. This Tree illustration has been first proposed by Darwin in the 19th century. This Tree of Life could be done by looking at physical traits. Now we have the ability to make a Tree of Life even more precise with the knowing of DNA.

Appendix 3, Picture A, represents Charles Darwin’s first diagram of an evolutionary tree from his “First Notebook on Transmutation of Species” (1837) is on view at the American Museum of Natural History in New York City.
It stands to reason that if the history of life forms a tree, with all species originating from a single trunk, then one can find a common origin for every existing species by tracing each twig (=existing species) back through its branches until they intersect at the branch they have in common. This node as we have seen is their common ancestor.
On Appendix 3, Picture B, we can see an example of an evolutionary Tree on which we can clearly see that each branch intercept a single common ancestor.

EXAMPLE

*'''See Appendix 3'''

==What is Natural selection?==
Natural selection is a process which requires that individuals of a species vary genetically in their ability to survive and reproduce in their environment.
In a more detailed way, if individuals within a species differ genetically from one another, and some of those differences affect the abilities of an individual to survive and reproduce in its environment, then in the next generation the “good” genes that lead to a higher survival and reproduction level will have relatively more copies than the “not so good” genes. Over time, the population will gradually become more and more suited to its environment as helpful mutations arise and spread through the population, while deleterious ones are weeded out. Ultimately, this process produces organisms that are well adapted to their habitats and way of life.

Let illustrate this process by a simple example. The woolly mammoth inhabited the northern parts Eurasia and North America, places were the weather can be especially cold. He was adapted to those extreme temperatures by bearing a thick coat of hair.
It probably descended from mammoth ancestors that had little hair. Mutations in the ancestral species led to some individuals being hairier than others. When the climate became cold the shaggy individuals were better able to tolerate their frigid surroundings and thus left more offspring than their balder fellows. By the way, the next generations will have a hairier average mammoth. Let this process continue over some thousands of generations and the smooth mammoth will be replaced by a shaggy one.
In Appendix 5, there is an illustration comparing a woolly mammoth and a modern elephant. A clear difference can be observed concerning the thickness of the hair of the mammoth especially on his ventral side.

Another example: Lamarck believed that giraffe's were no bigger than horses, but as there was little food around other than that on high up branches, a giraffe managed to stretch its neck and make it longer to reach the branches. When it mated, its offspring also had long necks. Ultimately, this process will continue through generations until our modern giraffe. Let look at APPENDIX ? --> MODIFICATION

*'''see Appendix 4'''

==What are the Nonselective mechanisms of evolutionary change?==
These mechanisms, also called ''genetic drift'', have nothing to do with adaptation; it is more about the random changes in the proportion of alleles due to the sampling effects of reproduction. Because natural selection is the only process that generates adaptation, the influence of the nonselective mechanisms of evolutionary change is less. This also helps us explain some neutral (nor useful or injurious) and non-adaptive features, like some DNA variations, even if we cannot prove that these features have absolutely no selective advantages. It can only play an evolutionary role on small population, and, because it has nothing to do with adaptation, it might sometimes just preserve bad alleles instead of destroying them, for example the high rate of genetically based diseases in small, isolated human communities, like Gaucher’s disease in northern Swedes.

=Can we consider Evolution as a theory?=
First of all, we have to make clear what a theory is: "A theory is a coherent group of tested general propositions, ''commonly regarded as correct'', that can be used as principles of explanation and prediction for a class of phenomena."
So in science, a theory is much more than only a supposition about how things are: it is a well-thought-out group of propositions meant to explain facts about the real world.

*'''see Appendix 5'''

=References=
*http://dictionary.reference.com/browse/theory
*http://en.wikipedia.org/wiki/Bipedalism

{{co|don't you think that you could bring some examples to illustrate this chapter which is a summary of the main points discussed in the book. The other option that would be even better would be to make LINKS with the other chapters (the other wiki pages)...}}--[[Utilisateur:Pierre.brawand|Pierre.brawand]] 30 mars 2012 à 10:57 (CEST)
{{co|Examples?}}--[[Utilisateur:Pierre.brawand|Pierre.brawand]] 25 avril 2012 à 18:28 (CEST)
----
*retour à [[Evolution_3BIbDF10-11_2011/12]] 
*retour à [[Accueil]]

WEIT 2012 Chap1

2012-04-27T13:44:34Z

MorganeV : /* Can we consider Evolution as a theory? */

<big>'''WHAT IS EVOLUTION'''</big> 
=What is the definition of Evolution?=

Evolution is a gradual process in which the biological populations change into a different and usually more complex or better form.
Life on Earth began with a universal common ancestor. It changed gradually, taking several millions of years.
This universal common ancestor, named LUCA (Last Universal Common Ancestor), branched out over time, throwing off many new and diverse species. This mechanism of evolutionary change is called natural selection. When you break that statement down, you find that it really consists of six components.

=What are the six components of the statement of evolution?=

The six components are '''evolution''', '''gradualism''', '''speciation''', '''common ancestry''', '''natural selection''', and '''nonselective mechanisms of evolutionary change'''. Let see each of these components closer.

==What is evolution?==
Evolution is the fact that a population of organisms undergoes genetic change over time. Individual organisms do not evolve.
The differences are based on the changes into the DNA, which originate as mutations. All the populations evolve but not at the same rate.
The theory of evolution doesn't predict that population will constantly be evolving, or how fast they will change when they do. It depends on the evolutionary pressures they experience.

*'''See Appendix 1'''

==What is gradualism?==
''Gradualism'' is the fact that it takes many generations to produce a substantial evolutionary change. The evolution of new features can take over hundreds or thousands (even millions) of generations. A species evolve faster or slower as evolutionary pressures wax and wane. Also, when the natural selection is strong, evolutionary change can be fast. But once a species becomes well adapted to a stable habitat, evolution often slows down.
Many living species share fundamental traits such as biochemical pathways that we use to produce energy, our standart four letters DNA code, and how that code is read and translated into proteins. This tells us that every species goes back to a single common ancestor (who had those traits and passed them on to its descendants).

Gradualism being evolutionary changes over time, it's often represented as a tree whose roots would be the common ancestor of all the species it represents . The difference between a gradualism and a punctuated equilibrium representation is that a punctuated equilibrium representation illustrats the evolutionary changes at given time and that graduilism one tries to show all the phases a spieces went trhough. In Appendix 4, there's a comparison of the two representations.

*'''See Appendix 2'''

==What is speciation?==
''Speciation'', also called ''splitting'', is a very slow process wich explains how a single ancestral species can split in several descendant species. More precisely, it's the appearence of slight differences between two different population of the same species and we consider that the splitting really occured when the differences become so important that the two population can no longer interbreed. Species themsleves cannot split and don't have to. This process doesn't happen quite often, but enough to explain us the great diversity of the terrestrial flora and fauna.
Since it doubles the number of opportunities for future speciation for a species, speciation might increase exponnentially the number of species, but more than 99 percent of the species did actually extinct without leaving any descendant.

One of the most interesting examples brings us millions years ago around the Triassic period and explains us the link between birds and reptiles or how a bipedal dinosaur, let’s call him ancestor X, split in order to give two new kinds of dinosaurs, one having actual reptiles’ features and producing bipedal, carnivorous dinosaurs, like the T.rex, and the other producing all the birds. This splitting would at first only be noticed by slight differences, like two population of the same species. We’ll have to wait thousands generations to see the dinosaur kind producing bird start flying.

This process is studied in a more detailed way in ch.7: "The Origin of Species".

==What is common ancestry?==
Common ancestry is the flip side of speciation. We can always look back in time, using either DNA sequences or fossils, and find descendants joining at their ancestors.
Every pair of species shares a common ancestor sometimes in the past.
To express the evolutionary relatedness among species through time, we use The Tree of Life. Tree which has been first proposed by Darwin in the 19th century. This Tree of Life could be done by looking at physical traits. Now we have the ability to make a Tree of Life even more precise with the knowing of DNA.

*'''See Appendix 3'''

==What is natural selection?==
Natural selection is a process which requires that individuals of a species vary genetically in their ability to survive and reproduce in their environment.
In a more detailed way, if individuals within a species differ genetically from one another, and some of those differences affect the abilities of an individual to survive and reproduce in its environment, then in the next generation the “good” genes that lead to a higher survival and reproduction level will have relatively more copies than the “not so good” genes. Over time, the population will gradually become more and more suited to its environment as helpful mutations arise and spread through the population, while deleterious ones are weeded out. Ultimately, this process produces organisms that are well adapted to their habitats and way of life.

Let illustrate this process by a simple example. The wooly mammoth inhabited the northern parts Eurasia and North America, places were the weather can be especially cold. He was adapted to those extreme temperatures by bearing a thick coat of hair.
It probably descended from mammoth ancestors that had little hair. Mutations in the ancestral species led to some individuals being hairier than others. When the climate became cold the shaggy individuals were better able to tolerate their frigid surroundings and thus left more offsprings than their balder fellows. By the way, the next generations will have a hairier average mammoth. Let this process continue over some thousands of generations and the smooth mammoth will be replaced by a shaggy one.
In Appendix 5, there is an illustration comparing a wooly mammoth and a modern elephant. A clear difference can be observed concerning the thickness of the hair of the mammoth especially on his ventral side.

*'''see Appendix 4'''

==What are the nonselective mechanisms of evolutionary change?==
These mechanisms, also called ''genetic drift'', have nothing to do with adaptation; it is more about the random changes in the proportion of alleles due to the sampling effects of reproduction. Because natural selection is the only process that generates adaptation, the influence of the nonselective mechanisms of evolutionary change is less. This also helps us explain some neutral (nor useful or injurious) and non-adaptive features, like some DNA variations, even if we cannot prove that these features have absolutely no selective advantages. It can only play an evolutionary role on small population, and, because it has nothing to do with adaptation, it might sometimes just preserve bad alleles instead of destroying them, for example the high rate of genetically based diseases in small, isolated human communities, like Gaucher’s disease in northern Swedes.

=Can we consider Evolution as a theory?=
First of all, we have to make clear what a theory is: "A theory is a coherent group of tested general propositions, ''commonly regarded as correct'', that can be used as principles of explanation and prediction for a class of phenomena."
So in science, a theory is much more than only a supposition about how things are: it is a well-thought-out group of propositions meant to explain facts about the real world.
Bec

*'''see Appendix 5'''

=References=
*http://dictionary.reference.com/browse/theory
*http://en.wikipedia.org/wiki/Bipedalism

{{co|don't you think that you could bring some examples to illustrate this chapter which is a summary of the main points discussed in the book. The other option that would be even better would be to make LINKS with the other chapters (the other wiki pages)...}}--[[Utilisateur:Pierre.brawand|Pierre.brawand]] 30 mars 2012 à 10:57 (CEST)
{{co|Examples?}}--[[Utilisateur:Pierre.brawand|Pierre.brawand]] 25 avril 2012 à 18:28 (CEST)
----
*retour à [[Evolution_3BIbDF10-11_2011/12]] 
*retour à [[Accueil]]

WEIT 2012 Chap1

2012-04-27T13:44:13Z

MorganeV : /* What is natural selection? */

<big>'''WHAT IS EVOLUTION'''</big> 
=What is the definition of Evolution?=

Evolution is a gradual process in which the biological populations change into a different and usually more complex or better form.
Life on Earth began with a universal common ancestor. It changed gradually, taking several millions of years.
This universal common ancestor, named LUCA (Last Universal Common Ancestor), branched out over time, throwing off many new and diverse species. This mechanism of evolutionary change is called natural selection. When you break that statement down, you find that it really consists of six components.

=What are the six components of the statement of evolution?=

The six components are '''evolution''', '''gradualism''', '''speciation''', '''common ancestry''', '''natural selection''', and '''nonselective mechanisms of evolutionary change'''. Let see each of these components closer.

==What is evolution?==
Evolution is the fact that a population of organisms undergoes genetic change over time. Individual organisms do not evolve.
The differences are based on the changes into the DNA, which originate as mutations. All the populations evolve but not at the same rate.
The theory of evolution doesn't predict that population will constantly be evolving, or how fast they will change when they do. It depends on the evolutionary pressures they experience.

*'''See Appendix 1'''

==What is gradualism?==
''Gradualism'' is the fact that it takes many generations to produce a substantial evolutionary change. The evolution of new features can take over hundreds or thousands (even millions) of generations. A species evolve faster or slower as evolutionary pressures wax and wane. Also, when the natural selection is strong, evolutionary change can be fast. But once a species becomes well adapted to a stable habitat, evolution often slows down.
Many living species share fundamental traits such as biochemical pathways that we use to produce energy, our standart four letters DNA code, and how that code is read and translated into proteins. This tells us that every species goes back to a single common ancestor (who had those traits and passed them on to its descendants).

Gradualism being evolutionary changes over time, it's often represented as a tree whose roots would be the common ancestor of all the species it represents . The difference between a gradualism and a punctuated equilibrium representation is that a punctuated equilibrium representation illustrats the evolutionary changes at given time and that graduilism one tries to show all the phases a spieces went trhough. In Appendix 4, there's a comparison of the two representations.

*'''See Appendix 2'''

==What is speciation?==
''Speciation'', also called ''splitting'', is a very slow process wich explains how a single ancestral species can split in several descendant species. More precisely, it's the appearence of slight differences between two different population of the same species and we consider that the splitting really occured when the differences become so important that the two population can no longer interbreed. Species themsleves cannot split and don't have to. This process doesn't happen quite often, but enough to explain us the great diversity of the terrestrial flora and fauna.
Since it doubles the number of opportunities for future speciation for a species, speciation might increase exponnentially the number of species, but more than 99 percent of the species did actually extinct without leaving any descendant.

One of the most interesting examples brings us millions years ago around the Triassic period and explains us the link between birds and reptiles or how a bipedal dinosaur, let’s call him ancestor X, split in order to give two new kinds of dinosaurs, one having actual reptiles’ features and producing bipedal, carnivorous dinosaurs, like the T.rex, and the other producing all the birds. This splitting would at first only be noticed by slight differences, like two population of the same species. We’ll have to wait thousands generations to see the dinosaur kind producing bird start flying.

This process is studied in a more detailed way in ch.7: "The Origin of Species".

==What is common ancestry?==
Common ancestry is the flip side of speciation. We can always look back in time, using either DNA sequences or fossils, and find descendants joining at their ancestors.
Every pair of species shares a common ancestor sometimes in the past.
To express the evolutionary relatedness among species through time, we use The Tree of Life. Tree which has been first proposed by Darwin in the 19th century. This Tree of Life could be done by looking at physical traits. Now we have the ability to make a Tree of Life even more precise with the knowing of DNA.

*'''See Appendix 3'''

==What is natural selection?==
Natural selection is a process which requires that individuals of a species vary genetically in their ability to survive and reproduce in their environment.
In a more detailed way, if individuals within a species differ genetically from one another, and some of those differences affect the abilities of an individual to survive and reproduce in its environment, then in the next generation the “good” genes that lead to a higher survival and reproduction level will have relatively more copies than the “not so good” genes. Over time, the population will gradually become more and more suited to its environment as helpful mutations arise and spread through the population, while deleterious ones are weeded out. Ultimately, this process produces organisms that are well adapted to their habitats and way of life.

Let illustrate this process by a simple example. The wooly mammoth inhabited the northern parts Eurasia and North America, places were the weather can be especially cold. He was adapted to those extreme temperatures by bearing a thick coat of hair.
It probably descended from mammoth ancestors that had little hair. Mutations in the ancestral species led to some individuals being hairier than others. When the climate became cold the shaggy individuals were better able to tolerate their frigid surroundings and thus left more offsprings than their balder fellows. By the way, the next generations will have a hairier average mammoth. Let this process continue over some thousands of generations and the smooth mammoth will be replaced by a shaggy one.
In Appendix 5, there is an illustration comparing a wooly mammoth and a modern elephant. A clear difference can be observed concerning the thickness of the hair of the mammoth especially on his ventral side.

*'''see Appendix 4'''

==What are the nonselective mechanisms of evolutionary change?==
These mechanisms, also called ''genetic drift'', have nothing to do with adaptation; it is more about the random changes in the proportion of alleles due to the sampling effects of reproduction. Because natural selection is the only process that generates adaptation, the influence of the nonselective mechanisms of evolutionary change is less. This also helps us explain some neutral (nor useful or injurious) and non-adaptive features, like some DNA variations, even if we cannot prove that these features have absolutely no selective advantages. It can only play an evolutionary role on small population, and, because it has nothing to do with adaptation, it might sometimes just preserve bad alleles instead of destroying them, for example the high rate of genetically based diseases in small, isolated human communities, like Gaucher’s disease in northern Swedes.

=Can we consider Evolution as a theory?=
First of all, we have to make clear what a theory is: "A theory is a coherent group of tested general propositions, ''commonly regarded as correct'', that can be used as principles of explanation and prediction for a class of phenomena."
So in science, a theory is much more than only a supposition about how things are: it is a well-thought-out group of propositions meant to explain facts about the real world.
Bec

*'''see Appendix 1'''

=References=
*http://dictionary.reference.com/browse/theory
*http://en.wikipedia.org/wiki/Bipedalism

{{co|don't you think that you could bring some examples to illustrate this chapter which is a summary of the main points discussed in the book. The other option that would be even better would be to make LINKS with the other chapters (the other wiki pages)...}}--[[Utilisateur:Pierre.brawand|Pierre.brawand]] 30 mars 2012 à 10:57 (CEST)
{{co|Examples?}}--[[Utilisateur:Pierre.brawand|Pierre.brawand]] 25 avril 2012 à 18:28 (CEST)
----
*retour à [[Evolution_3BIbDF10-11_2011/12]] 
*retour à [[Accueil]]

WEIT 2012 Chap1

2012-04-27T13:43:49Z

MorganeV : /* What is common ancestry? */

<big>'''WHAT IS EVOLUTION'''</big> 
=What is the definition of Evolution?=

Evolution is a gradual process in which the biological populations change into a different and usually more complex or better form.
Life on Earth began with a universal common ancestor. It changed gradually, taking several millions of years.
This universal common ancestor, named LUCA (Last Universal Common Ancestor), branched out over time, throwing off many new and diverse species. This mechanism of evolutionary change is called natural selection. When you break that statement down, you find that it really consists of six components.

=What are the six components of the statement of evolution?=

The six components are '''evolution''', '''gradualism''', '''speciation''', '''common ancestry''', '''natural selection''', and '''nonselective mechanisms of evolutionary change'''. Let see each of these components closer.

==What is evolution?==
Evolution is the fact that a population of organisms undergoes genetic change over time. Individual organisms do not evolve.
The differences are based on the changes into the DNA, which originate as mutations. All the populations evolve but not at the same rate.
The theory of evolution doesn't predict that population will constantly be evolving, or how fast they will change when they do. It depends on the evolutionary pressures they experience.

*'''See Appendix 1'''

==What is gradualism?==
''Gradualism'' is the fact that it takes many generations to produce a substantial evolutionary change. The evolution of new features can take over hundreds or thousands (even millions) of generations. A species evolve faster or slower as evolutionary pressures wax and wane. Also, when the natural selection is strong, evolutionary change can be fast. But once a species becomes well adapted to a stable habitat, evolution often slows down.
Many living species share fundamental traits such as biochemical pathways that we use to produce energy, our standart four letters DNA code, and how that code is read and translated into proteins. This tells us that every species goes back to a single common ancestor (who had those traits and passed them on to its descendants).

Gradualism being evolutionary changes over time, it's often represented as a tree whose roots would be the common ancestor of all the species it represents . The difference between a gradualism and a punctuated equilibrium representation is that a punctuated equilibrium representation illustrats the evolutionary changes at given time and that graduilism one tries to show all the phases a spieces went trhough. In Appendix 4, there's a comparison of the two representations.

*'''See Appendix 2'''

==What is speciation?==
''Speciation'', also called ''splitting'', is a very slow process wich explains how a single ancestral species can split in several descendant species. More precisely, it's the appearence of slight differences between two different population of the same species and we consider that the splitting really occured when the differences become so important that the two population can no longer interbreed. Species themsleves cannot split and don't have to. This process doesn't happen quite often, but enough to explain us the great diversity of the terrestrial flora and fauna.
Since it doubles the number of opportunities for future speciation for a species, speciation might increase exponnentially the number of species, but more than 99 percent of the species did actually extinct without leaving any descendant.

One of the most interesting examples brings us millions years ago around the Triassic period and explains us the link between birds and reptiles or how a bipedal dinosaur, let’s call him ancestor X, split in order to give two new kinds of dinosaurs, one having actual reptiles’ features and producing bipedal, carnivorous dinosaurs, like the T.rex, and the other producing all the birds. This splitting would at first only be noticed by slight differences, like two population of the same species. We’ll have to wait thousands generations to see the dinosaur kind producing bird start flying.

This process is studied in a more detailed way in ch.7: "The Origin of Species".

==What is common ancestry?==
Common ancestry is the flip side of speciation. We can always look back in time, using either DNA sequences or fossils, and find descendants joining at their ancestors.
Every pair of species shares a common ancestor sometimes in the past.
To express the evolutionary relatedness among species through time, we use The Tree of Life. Tree which has been first proposed by Darwin in the 19th century. This Tree of Life could be done by looking at physical traits. Now we have the ability to make a Tree of Life even more precise with the knowing of DNA.

*'''See Appendix 3'''

==What is natural selection?==
Natural selection is a process which requires that individuals of a species vary genetically in their ability to survive and reproduce in their environment.
In a more detailed way, if individuals within a species differ genetically from one another, and some of those differences affect the abilities of an individual to survive and reproduce in its environment, then in the next generation the “good” genes that lead to a higher survival and reproduction level will have relatively more copies than the “not so good” genes. Over time, the population will gradually become more and more suited to its environment as helpful mutations arise and spread through the population, while deleterious ones are weeded out. Ultimately, this process produces organisms that are well adapted to their habitats and way of life.

Let illustrate this process by a simple example. The wooly mammoth inhabited the northern parts Eurasia and North America, places were the weather can be especially cold. He was adapted to those extreme temperatures by bearing a thick coat of hair.
It probably descended from mammoth ancestors that had little hair. Mutations in the ancestral species led to some individuals being hairier than others. When the climate became cold the shaggy individuals were better able to tolerate their frigid surroundings and thus left more offsprings than their balder fellows. By the way, the next generations will have a hairier average mammoth. Let this process continue over some thousands of generations and the smooth mammoth will be replaced by a shaggy one.
In Appendix 5, there is an illustration comparing a wooly mammoth and a modern elephant. A clear difference can be observed concerning the thickness of the hair of the mammoth especially on his ventral side.

*'''see Appendix 5'''

==What are the nonselective mechanisms of evolutionary change?==
These mechanisms, also called ''genetic drift'', have nothing to do with adaptation; it is more about the random changes in the proportion of alleles due to the sampling effects of reproduction. Because natural selection is the only process that generates adaptation, the influence of the nonselective mechanisms of evolutionary change is less. This also helps us explain some neutral (nor useful or injurious) and non-adaptive features, like some DNA variations, even if we cannot prove that these features have absolutely no selective advantages. It can only play an evolutionary role on small population, and, because it has nothing to do with adaptation, it might sometimes just preserve bad alleles instead of destroying them, for example the high rate of genetically based diseases in small, isolated human communities, like Gaucher’s disease in northern Swedes.

=Can we consider Evolution as a theory?=
First of all, we have to make clear what a theory is: "A theory is a coherent group of tested general propositions, ''commonly regarded as correct'', that can be used as principles of explanation and prediction for a class of phenomena."
So in science, a theory is much more than only a supposition about how things are: it is a well-thought-out group of propositions meant to explain facts about the real world.
Bec

*'''see Appendix 1'''

=References=
*http://dictionary.reference.com/browse/theory
*http://en.wikipedia.org/wiki/Bipedalism

{{co|don't you think that you could bring some examples to illustrate this chapter which is a summary of the main points discussed in the book. The other option that would be even better would be to make LINKS with the other chapters (the other wiki pages)...}}--[[Utilisateur:Pierre.brawand|Pierre.brawand]] 30 mars 2012 à 10:57 (CEST)
{{co|Examples?}}--[[Utilisateur:Pierre.brawand|Pierre.brawand]] 25 avril 2012 à 18:28 (CEST)
----
*retour à [[Evolution_3BIbDF10-11_2011/12]] 
*retour à [[Accueil]]

WEIT 2012 Chap1

2012-04-27T13:43:03Z

MorganeV : /* What is gradualism? */

<big>'''WHAT IS EVOLUTION'''</big> 
=What is the definition of Evolution?=

Evolution is a gradual process in which the biological populations change into a different and usually more complex or better form.
Life on Earth began with a universal common ancestor. It changed gradually, taking several millions of years.
This universal common ancestor, named LUCA (Last Universal Common Ancestor), branched out over time, throwing off many new and diverse species. This mechanism of evolutionary change is called natural selection. When you break that statement down, you find that it really consists of six components.

=What are the six components of the statement of evolution?=

The six components are '''evolution''', '''gradualism''', '''speciation''', '''common ancestry''', '''natural selection''', and '''nonselective mechanisms of evolutionary change'''. Let see each of these components closer.

==What is evolution?==
Evolution is the fact that a population of organisms undergoes genetic change over time. Individual organisms do not evolve.
The differences are based on the changes into the DNA, which originate as mutations. All the populations evolve but not at the same rate.
The theory of evolution doesn't predict that population will constantly be evolving, or how fast they will change when they do. It depends on the evolutionary pressures they experience.

*'''See Appendix 1'''

==What is gradualism?==
''Gradualism'' is the fact that it takes many generations to produce a substantial evolutionary change. The evolution of new features can take over hundreds or thousands (even millions) of generations. A species evolve faster or slower as evolutionary pressures wax and wane. Also, when the natural selection is strong, evolutionary change can be fast. But once a species becomes well adapted to a stable habitat, evolution often slows down.
Many living species share fundamental traits such as biochemical pathways that we use to produce energy, our standart four letters DNA code, and how that code is read and translated into proteins. This tells us that every species goes back to a single common ancestor (who had those traits and passed them on to its descendants).

Gradualism being evolutionary changes over time, it's often represented as a tree whose roots would be the common ancestor of all the species it represents . The difference between a gradualism and a punctuated equilibrium representation is that a punctuated equilibrium representation illustrats the evolutionary changes at given time and that graduilism one tries to show all the phases a spieces went trhough. In Appendix 4, there's a comparison of the two representations.

*'''See Appendix 2'''

==What is speciation?==
''Speciation'', also called ''splitting'', is a very slow process wich explains how a single ancestral species can split in several descendant species. More precisely, it's the appearence of slight differences between two different population of the same species and we consider that the splitting really occured when the differences become so important that the two population can no longer interbreed. Species themsleves cannot split and don't have to. This process doesn't happen quite often, but enough to explain us the great diversity of the terrestrial flora and fauna.
Since it doubles the number of opportunities for future speciation for a species, speciation might increase exponnentially the number of species, but more than 99 percent of the species did actually extinct without leaving any descendant.

One of the most interesting examples brings us millions years ago around the Triassic period and explains us the link between birds and reptiles or how a bipedal dinosaur, let’s call him ancestor X, split in order to give two new kinds of dinosaurs, one having actual reptiles’ features and producing bipedal, carnivorous dinosaurs, like the T.rex, and the other producing all the birds. This splitting would at first only be noticed by slight differences, like two population of the same species. We’ll have to wait thousands generations to see the dinosaur kind producing bird start flying.

This process is studied in a more detailed way in ch.7: "The Origin of Species".

==What is common ancestry?==
Common ancestry is the flip side of speciation. We can always look back in time, using either DNA sequences or fossils, and find descendants joining at their ancestors.
Every pair of species shares a common ancestor sometimes in the past.
To express the evolutionary relatedness among species through time, we use The Tree of Life. Tree which has been first proposed by Darwin in the 19th century. This Tree of Life could be done by looking at physical traits. Now we have the ability to make a Tree of Life even more precise with the knowing of DNA.

*'''See Appendix 2'''

==What is natural selection?==
Natural selection is a process which requires that individuals of a species vary genetically in their ability to survive and reproduce in their environment.
In a more detailed way, if individuals within a species differ genetically from one another, and some of those differences affect the abilities of an individual to survive and reproduce in its environment, then in the next generation the “good” genes that lead to a higher survival and reproduction level will have relatively more copies than the “not so good” genes. Over time, the population will gradually become more and more suited to its environment as helpful mutations arise and spread through the population, while deleterious ones are weeded out. Ultimately, this process produces organisms that are well adapted to their habitats and way of life.

Let illustrate this process by a simple example. The wooly mammoth inhabited the northern parts Eurasia and North America, places were the weather can be especially cold. He was adapted to those extreme temperatures by bearing a thick coat of hair.
It probably descended from mammoth ancestors that had little hair. Mutations in the ancestral species led to some individuals being hairier than others. When the climate became cold the shaggy individuals were better able to tolerate their frigid surroundings and thus left more offsprings than their balder fellows. By the way, the next generations will have a hairier average mammoth. Let this process continue over some thousands of generations and the smooth mammoth will be replaced by a shaggy one.
In Appendix 5, there is an illustration comparing a wooly mammoth and a modern elephant. A clear difference can be observed concerning the thickness of the hair of the mammoth especially on his ventral side.

*'''see Appendix 5'''

==What are the nonselective mechanisms of evolutionary change?==
These mechanisms, also called ''genetic drift'', have nothing to do with adaptation; it is more about the random changes in the proportion of alleles due to the sampling effects of reproduction. Because natural selection is the only process that generates adaptation, the influence of the nonselective mechanisms of evolutionary change is less. This also helps us explain some neutral (nor useful or injurious) and non-adaptive features, like some DNA variations, even if we cannot prove that these features have absolutely no selective advantages. It can only play an evolutionary role on small population, and, because it has nothing to do with adaptation, it might sometimes just preserve bad alleles instead of destroying them, for example the high rate of genetically based diseases in small, isolated human communities, like Gaucher’s disease in northern Swedes.

=Can we consider Evolution as a theory?=
First of all, we have to make clear what a theory is: "A theory is a coherent group of tested general propositions, ''commonly regarded as correct'', that can be used as principles of explanation and prediction for a class of phenomena."
So in science, a theory is much more than only a supposition about how things are: it is a well-thought-out group of propositions meant to explain facts about the real world.
Bec

*'''see Appendix 1'''

=References=
*http://dictionary.reference.com/browse/theory
*http://en.wikipedia.org/wiki/Bipedalism

{{co|don't you think that you could bring some examples to illustrate this chapter which is a summary of the main points discussed in the book. The other option that would be even better would be to make LINKS with the other chapters (the other wiki pages)...}}--[[Utilisateur:Pierre.brawand|Pierre.brawand]] 30 mars 2012 à 10:57 (CEST)
{{co|Examples?}}--[[Utilisateur:Pierre.brawand|Pierre.brawand]] 25 avril 2012 à 18:28 (CEST)
----
*retour à [[Evolution_3BIbDF10-11_2011/12]] 
*retour à [[Accueil]]

WEIT 2012 Chap1

2012-04-27T13:41:17Z

MorganeV : /* What is evolution? */

<big>'''WHAT IS EVOLUTION'''</big> 
=What is the definition of Evolution?=

Evolution is a gradual process in which the biological populations change into a different and usually more complex or better form.
Life on Earth began with a universal common ancestor. It changed gradually, taking several millions of years.
This universal common ancestor, named LUCA (Last Universal Common Ancestor), branched out over time, throwing off many new and diverse species. This mechanism of evolutionary change is called natural selection. When you break that statement down, you find that it really consists of six components.

=What are the six components of the statement of evolution?=

The six components are '''evolution''', '''gradualism''', '''speciation''', '''common ancestry''', '''natural selection''', and '''nonselective mechanisms of evolutionary change'''. Let see each of these components closer.

==What is evolution?==
Evolution is the fact that a population of organisms undergoes genetic change over time. Individual organisms do not evolve.
The differences are based on the changes into the DNA, which originate as mutations. All the populations evolve but not at the same rate.
The theory of evolution doesn't predict that population will constantly be evolving, or how fast they will change when they do. It depends on the evolutionary pressures they experience.

*'''See Appendix 1'''

==What is gradualism?==
''Gradualism'' is the fact that it takes many generations to produce a substantial evolutionary change. The evolution of new features can take over hundreds or thousands (even millions) of generations. A species evolve faster or slower as evolutionary pressures wax and wane. Also, when the natural selection is strong, evolutionary change can be fast. But once a species becomes well adapted to a stable habitat, evolution often slows down.
Many living species share fundamental traits such as biochemical pathways that we use to produce energy, our standart four letters DNA code, and how that code is read and translated into proteins. This tells us that every species goes back to a single common ancestor (who had those traits and passed them on to its descendants).

Gradualism being evolutionary changes over time, it's often represented as a tree whose roots would be the common ancestor of all the species it represents . The difference between a gradualism and a punctuated equilibrium representation is that a punctuated equilibrium representation illustrats the evolutionary changes at given time and that graduilism one tries to show all the phases a spieces went trhough. In Appendix 4, there's a comparison of the two representations.

*'''See Appendix 4'''

==What is speciation?==
''Speciation'', also called ''splitting'', is a very slow process wich explains how a single ancestral species can split in several descendant species. More precisely, it's the appearence of slight differences between two different population of the same species and we consider that the splitting really occured when the differences become so important that the two population can no longer interbreed. Species themsleves cannot split and don't have to. This process doesn't happen quite often, but enough to explain us the great diversity of the terrestrial flora and fauna.
Since it doubles the number of opportunities for future speciation for a species, speciation might increase exponnentially the number of species, but more than 99 percent of the species did actually extinct without leaving any descendant.

One of the most interesting examples brings us millions years ago around the Triassic period and explains us the link between birds and reptiles or how a bipedal dinosaur, let’s call him ancestor X, split in order to give two new kinds of dinosaurs, one having actual reptiles’ features and producing bipedal, carnivorous dinosaurs, like the T.rex, and the other producing all the birds. This splitting would at first only be noticed by slight differences, like two population of the same species. We’ll have to wait thousands generations to see the dinosaur kind producing bird start flying.

This process is studied in a more detailed way in ch.7: "The Origin of Species".

==What is common ancestry?==
Common ancestry is the flip side of speciation. We can always look back in time, using either DNA sequences or fossils, and find descendants joining at their ancestors.
Every pair of species shares a common ancestor sometimes in the past.
To express the evolutionary relatedness among species through time, we use The Tree of Life. Tree which has been first proposed by Darwin in the 19th century. This Tree of Life could be done by looking at physical traits. Now we have the ability to make a Tree of Life even more precise with the knowing of DNA.

*'''See Appendix 2'''

==What is natural selection?==
Natural selection is a process which requires that individuals of a species vary genetically in their ability to survive and reproduce in their environment.
In a more detailed way, if individuals within a species differ genetically from one another, and some of those differences affect the abilities of an individual to survive and reproduce in its environment, then in the next generation the “good” genes that lead to a higher survival and reproduction level will have relatively more copies than the “not so good” genes. Over time, the population will gradually become more and more suited to its environment as helpful mutations arise and spread through the population, while deleterious ones are weeded out. Ultimately, this process produces organisms that are well adapted to their habitats and way of life.

Let illustrate this process by a simple example. The wooly mammoth inhabited the northern parts Eurasia and North America, places were the weather can be especially cold. He was adapted to those extreme temperatures by bearing a thick coat of hair.
It probably descended from mammoth ancestors that had little hair. Mutations in the ancestral species led to some individuals being hairier than others. When the climate became cold the shaggy individuals were better able to tolerate their frigid surroundings and thus left more offsprings than their balder fellows. By the way, the next generations will have a hairier average mammoth. Let this process continue over some thousands of generations and the smooth mammoth will be replaced by a shaggy one.
In Appendix 5, there is an illustration comparing a wooly mammoth and a modern elephant. A clear difference can be observed concerning the thickness of the hair of the mammoth especially on his ventral side.

*'''see Appendix 5'''

==What are the nonselective mechanisms of evolutionary change?==
These mechanisms, also called ''genetic drift'', have nothing to do with adaptation; it is more about the random changes in the proportion of alleles due to the sampling effects of reproduction. Because natural selection is the only process that generates adaptation, the influence of the nonselective mechanisms of evolutionary change is less. This also helps us explain some neutral (nor useful or injurious) and non-adaptive features, like some DNA variations, even if we cannot prove that these features have absolutely no selective advantages. It can only play an evolutionary role on small population, and, because it has nothing to do with adaptation, it might sometimes just preserve bad alleles instead of destroying them, for example the high rate of genetically based diseases in small, isolated human communities, like Gaucher’s disease in northern Swedes.

=Can we consider Evolution as a theory?=
First of all, we have to make clear what a theory is: "A theory is a coherent group of tested general propositions, ''commonly regarded as correct'', that can be used as principles of explanation and prediction for a class of phenomena."
So in science, a theory is much more than only a supposition about how things are: it is a well-thought-out group of propositions meant to explain facts about the real world.
Bec

*'''see Appendix 1'''

=References=
*http://dictionary.reference.com/browse/theory
*http://en.wikipedia.org/wiki/Bipedalism

{{co|don't you think that you could bring some examples to illustrate this chapter which is a summary of the main points discussed in the book. The other option that would be even better would be to make LINKS with the other chapters (the other wiki pages)...}}--[[Utilisateur:Pierre.brawand|Pierre.brawand]] 30 mars 2012 à 10:57 (CEST)
{{co|Examples?}}--[[Utilisateur:Pierre.brawand|Pierre.brawand]] 25 avril 2012 à 18:28 (CEST)
----
*retour à [[Evolution_3BIbDF10-11_2011/12]] 
*retour à [[Accueil]]

WEIT 2012 Chap1

2012-03-30T13:52:43Z

MorganeV : /* What is evolution? */

WEIT 2012 Chap1

2012-03-30T13:47:38Z

MorganeV : /* What is common ancestry? */

WEIT 2012 Chap1

2012-03-30T13:31:57Z

MorganeV : /* What is common ancestry? */

WEIT 2012 Chap1

2012-03-16T15:12:04Z

MorganeV : /* What is gradualism? */

WEIT 2012 Chap1

2012-03-16T14:42:42Z

MorganeV : /* What is evolution? */

WEIT 2012 Chap1

2012-03-16T14:37:29Z

MorganeV : /* What is evolution? */

WEIT 2012 Chap1

2012-03-16T14:31:29Z

MorganeV : /* What is the definition of Evolution? */

WEIT 2012 Chap1

2012-03-16T14:26:29Z

MorganeV : /* What is the definition of Evolution? */

WEIT 2012 Chap1

2012-03-09T15:39:19Z

MorganeV : /* What is the definition of Evolution? */

<big>'''WHAT IS EVOLUTION'''</big> 
=What is the definition of Evolution?=

Evolution is a gradual process in which something changes into a different and usually more complex or better form.

Life on earth began with one primitive species. It changed gradually, taking several millions of years.
This one species branched out over time, throwing off many new and diverse species. This mechanism of evolutionary change is called natural selection. When you break that statement down, you find that it really consists of six components.

=What are the six components?=

The six components are evolution, gradualism, speciation, common ancestry, natural selection, and nonselective mechanisms of evolutionary change. Let see each of these components closer.

==What is evolution?==
==What is gradualism?==
==What is speciation?==
==What is common ancestry?==
==What is natural selection?==
==What is nonselective mechanisms of evolutionary change?==

WEIT 2012 Chap1

2012-03-09T15:34:36Z

MorganeV : /* What is the definition of Evolution? */

<big>'''WHAT IS EVOLUTION'''</big> 
=What is the definition of Evolution?=

Evolution is a gradual process in which something changes into a different and usually more complex or better form.

Life on earth changed gradually, beginning with one primitive species. Taking millions of years, it branched out over time, throwing off many new and diverse species. This mechanism of evolutionary change is called natural selection. When you break that statement down, you find that it really consists of six components.

=What are the six components?=

The six components are evolution, gradualism, speciation, common ancestry, natural selection, and nonselective mechanisms of evolutionary change. Let see each of these components closer.

==What is evolution?==
==What is gradualism?==
==What is speciation?==
==What is common ancestry?==
==What is natural selection?==
==What is nonselective mechanisms of evolutionary change?==

WEIT 2012 Chap1

2012-03-09T15:20:17Z

MorganeV : /* What are these six components? */

WEIT 2012 Chap1

2012-03-09T15:18:01Z

MorganeV : /* What are these six components? */

<big>'''WHAT IS EVOLUTION'''</big> 
=What is the definition of Evolution?=

Evolution is a gradual process in which something changes into a different and usually more complex or better form.

Life on earth changed gradually, beginning with one primitive species. Taking millions of years, it branched out over time, throwing off many new and diverse species. This mechanism of evolutionary change is called natural selection.
When you break that statement down, you find that that it really consists of six components.

=What are these six components?=

The six components are evolution, gradualism, speciation, common ancestry, natural selection, and nonselective mechanisms of evolutionary change.

*retour à [[Evolution_3BIbDF10-11_2011/12]] 
*retour à [[Accueil]]

WEIT 2012 Chap1

2012-03-09T15:16:05Z

MorganeV : /* What is the definition of Evolution? */

WEIT 2012 Chap1

2012-03-09T14:39:28Z

MorganeV :

<big>'''WHAT IS EVOLUTION'''</big> 
=What is the definition of Evolution?=
----
*retour à [[Evolution_3BIbDF10-11_2011/12]] 
*retour à [[Accueil]]

Consignes

2012-03-09T14:19:48Z

MorganeV : /* 3BIbDF10&11 */

== Rédaction d'une page Wiki ==

Le but principal est de rédiger une page sous la forme de questions-réponses.

*Chaque question se traduira sous la forme d'un titre: il faut donc veiller à utiliser des titres explicites
*Plus la question sera précise et plus la réponse sera courte et facile à donner. Il faut donc définir les bonnes questions!
*Hiérarchiser les titres: posez-vous d'abord telle question, puis telle autre, etc.
*La réponse à une question va souvent vous servir de base pour une nouvelle question... et le cycle continue!
*Indiquez systématiquement la source de vos informations: URL, source bibliographique, etc.
*Variez vos sources en puisant dans les différents supports à disposition: livres, revues, articles, internet, etc.
*Tenez compte de ce qui a déjà été écrit sur le Wiki: ce n'est pas la peine de répéter inutilement des informations: une lecture préalable de la page s'imposera donc pour savoir où vous en êtes!
*Attention à l'orthographe et la syntaxe... ce que vous écrivez doit être lisible par tous!
*Datez et signez vos contributions à l'aide de: <nowiki>~~~~ (4 tildes)</nowiki>= [[Utilisateur:Pierre.brawand|Pierre.brawand]] 27 août 2006 à 21:29 (MEST)

== Correction des pages Wiki ==
Vos pages seront corrigées régulièrement de la manière suivante! La ''couleur verte italique '' indiquera une correction de vos '''enseignants exclusivement'''.

Exemple:
 
L'Homme descend du Singe et le Singe descend de l'arbre...
 

{{co|Tout porte à croire que l'Homme descende du Singe et que donc, tous deux, aient un ancêtre commun relativement proche...}}

A vous de tenir compte des corrections en reformulant vos propos afin d'améliorer votre document!

Veuillez dans ce cas enlever le code de formatage de {{co|couleur verte italique}} utilisé par vos enseignants.

== Statut du document ==
*Le document lui-même n'est pas important, c'est ce qui a pu être construit à l'intérieur des élèves par toutes les étapes de l'activité qui est important. (F. Lombard)

*En d'autres termes... c'est le travail que vous produirez ensemble dans la mise sur pied du document qui vous sera utile à la compréhension du sujet.
*Ne perdez donc pas de temps à "formater" vos pages inutilement...

==Traitement des images==

Pour des raisons évidentes et légales, il n'est pas possible de charger nos pages Wiki avec des images.
Pourtant celles-ci sont particulièrement utiles à la bonne compréhension de certains mécanismes biologiques complexes...

Vous pouvez sans problème contourner ce problème de la manière suivante:

*dans la page Wiki, indiquez le lien de l'image si celle-ci a été prise sur Internet: ce lien permettra d'accéder à l'image "en ligne".
*copiez l'image sur le dossier Doc_annexes.doc qui se trouve sur le serveur Mimosa et renommer le fichier en indiquant le numéro de cours suivi du numéro de l'annexe:
::Exemple: '''4BIOS01_Annexe3.doc'''
*Complétez sur le document les points suivants:
:*le numéro de l'annexe
:*le titre de l'image
:*votre prénom
:*la source
:*un commentaire (légende explicative, etc.)
*Ce fichier word, sera ensuite imprimé et rajouter sous forme d'annexe au futur polycopié.
[[Utilisateur:Pierre.brawand|Pierre.brawand]] 25 septembre 2006 à 23:06 (MEST)

== Présentations orales ==
*Répartissez-vous le temps de parole entre les différents membres du groupe
*Partagez-vous les différentes parties de la présentation
*Indiquez le titre de votre présentation et son contexte (quel chapitre, ou quelle partie de chapitre, etc.)
*Exposez au préalable le plan de votre présentation: qui va parler de quoi et pourquoi!
*Description des résultats: projetez tout d'abord la page Wiki puis peut-être illustrez vos propos à l'aide d'une figure (en indiquant les sources)
*Exposez l'état de vos recherches: à l'heure actuelle de nos recherches, nous en sommes là... mais la semaine prochaine nous en serons peut-être là... Surtout, ne pas fermer les portes... il est normal que vous ne maitrisiez pas tout le sujet dès le début.
*Pour les présentations finales (qui seront généralement évaluées), prévoyez un support multimédia de type présentation Power Point avec au maximum 10 diapos. Prévoyez une diapositive d'introduction ainsi qu'une pour la conclusion.
*Faites des liens si possible avec les présentations des autres groupes
*Conclusions: la partie la plus intéressante! Elle doit permettre de soulever des questions chez vos auditeurs!
*Réponses aux questions: écoutez bien les questions... et réfléchissez quelques secondes avant de répondre. Soyez le plus clair possible dans votre réponse. Au besoin, répétez vos propos.
 
:''Site intéressant donnant des conseils pour l'élaboration du présentation orale scientifique.''
:*http://www.ipmc.cnrs.fr/~duprat/techcom/oral.htm#debut

==Elaboration des posters==
:''Quelques sites intéressants donnant des conseils pour l'élaboration des posters.''
:*http://www.ipmc.cnrs.fr/~duprat/techcom/poster.htm#conseil
:*http://mdc2007.fpms.ac.be/documents/posters.pdf
:*http://www4.utc.fr/~sp01/Fiches%20Pratiques/Consignes%20Poster.pdf

== Evaluation ==

L'évaluation portera sur différents aspects:

*Participation à la création des pages
*Connaissances acquises = tests de connaissances
*Aptitudes à transposer vos connaissances dans un situation particulière = tests d'aptitudes

*Présentations orales en classe:
**Plan de la présentation
**Clarté, concision, précision
**Vulgarisation
**Résultats
**Questions soulevées (débat)

==Rapports de laboratoire==

Quelques conseils pour l'écriture de vos rapports de biologie...
Suivez le plan suivant en indiquant les différentes rubriques

*'''Titre:'''
**Donner un titre général au laboratoire

*'''Introduction:'''
**Décrire le but de l'expérience ou de l'observation.
::*expérimentation: décrire le problème posé et résumer les travaux ou les connaissances précédents.
::*observations: décrire l'objet qui va être observé et ajouter quelques notes (provenance, mode de vie, etc…)

*'''Matériel et Méthodes:'''
**Technique utilisée
**Matériel nécessaire ou à disposition: liste précise des équipements, origine, lieu d'observation, date, météo, etc…
**Dessins et plans si nécessaire.

*'''Résultats:'''
**Penser à introduire vos résultats et à les exposer.
**Sous forme de tableaux, graphiques, dessins, avec légende ou texte explicatif.
**Vos résultats doivent être statistiquement valables… donc comparez-les à ceux de vos camarades de classe ou répéter l'expérience suffisamment de fois!
**Ne rien discuter ni commenter dans cette rubrique. Il s'agit ici uniquement de présenter les résultats.

*'''Discussion:'''
**Relier les résultats obtenus au but initial de l'expérience ou de l'observation.
**Interpréter les résultats en les reliant aux connaissances actuelles.
**Définir et proposer un éventuel modèle qui pourrait expliquer les résultats obtenus.

*'''Conclusion:'''
**Proposer d'autres expériences à faire afin de poursuivre l'étude de manière plus complète.
**Placer le travail dans un contexte plus large, discuter des conséquences, des implications, etc…
**La Conclusion peut être liée directement avec la partie Discussion sous forme de Discussion/Conclusion.

*'''Remarques:'''
**rendre un rapport propre, clair
**soigner la présentation: rapport dactylographié, entête comprenant: nom prénom, groupe, date
**résultats explicitement présentés
**textes des légendes écrits droits et reliés au dessin par un trait tiré à la règle
**dessins clairs et précis, suffisamment grands, en utilisant un bon crayon

 [[Utilisateur:Pierre.brawand|Pierre.brawand]] 19 septembre 2008 à 21:59 (MEST)

== Signatures ==
*Datez et signez vos contributions à l'aide de: <nowiki>~~~~ (4 tildes)</nowiki> que vous placerez après "lu et approuvé:"
*Ecrivez <nowiki> </nowiki> en fin de ligne pour faire un saut de ligne simple
===3BIbDF10&11===
lu et approuvé: --[[Utilisateur:Pierre.brawand|Pierre.brawand]] 2 mars 2012 à 16:17 (CET) 
lu et approuvé: --[[Utilisateur:CarolineZ|CarolineZ]] 8 mars 2012 à 09:01 (CET) 
lu et approuvé: --[[Utilisateur:MarigonaK|MarigonaK]] 8 mars 2012 à 09:25 (CET) 
lu et approuvé: --[[Utilisateur:AgnesP|AgnesP]] 9 mars 2012 à 07:05 (CET) 
lu et approuvé: [[Utilisateur:AlexanderE|AlexanderE]] 9 mars 2012 à 15:17 (CET)

lu et approuvé: --[[Utilisateur:MorganeV|MorganeV]]
lu et approuvé: 
lu et approuvé: 
lu et approuvé: 

===2BIOS01&02&03===
lu et approuvé: --[[Utilisateur:Pierre.brawand|Pierre.brawand]] 9 mars 2012 à 14:48 (CET) 
lu et approuvé: 
lu et approuvé: 
lu et approuvé: 
lu et approuvé: 
lu et approuvé: 
lu et approuvé: 
lu et approuvé: 
lu et approuvé: 
lu et approuvé: 
lu et approuvé: 
lu et approuvé: 
lu et approuvé: 
lu et approuvé: 
lu et approuvé: 

----
retour à [[Accueil]]

Consignes

2012-03-09T14:18:20Z

MorganeV : /* 3BIbDF10&11 */

== Rédaction d'une page Wiki ==

Le but principal est de rédiger une page sous la forme de questions-réponses.

*Chaque question se traduira sous la forme d'un titre: il faut donc veiller à utiliser des titres explicites
*Plus la question sera précise et plus la réponse sera courte et facile à donner. Il faut donc définir les bonnes questions!
*Hiérarchiser les titres: posez-vous d'abord telle question, puis telle autre, etc.
*La réponse à une question va souvent vous servir de base pour une nouvelle question... et le cycle continue!
*Indiquez systématiquement la source de vos informations: URL, source bibliographique, etc.
*Variez vos sources en puisant dans les différents supports à disposition: livres, revues, articles, internet, etc.
*Tenez compte de ce qui a déjà été écrit sur le Wiki: ce n'est pas la peine de répéter inutilement des informations: une lecture préalable de la page s'imposera donc pour savoir où vous en êtes!
*Attention à l'orthographe et la syntaxe... ce que vous écrivez doit être lisible par tous!
*Datez et signez vos contributions à l'aide de: <nowiki>~~~~ (4 tildes)</nowiki>= [[Utilisateur:Pierre.brawand|Pierre.brawand]] 27 août 2006 à 21:29 (MEST)

== Correction des pages Wiki ==
Vos pages seront corrigées régulièrement de la manière suivante! La ''couleur verte italique '' indiquera une correction de vos '''enseignants exclusivement'''.

Exemple:
 
L'Homme descend du Singe et le Singe descend de l'arbre...
 

{{co|Tout porte à croire que l'Homme descende du Singe et que donc, tous deux, aient un ancêtre commun relativement proche...}}

A vous de tenir compte des corrections en reformulant vos propos afin d'améliorer votre document!

Veuillez dans ce cas enlever le code de formatage de {{co|couleur verte italique}} utilisé par vos enseignants.

== Statut du document ==
*Le document lui-même n'est pas important, c'est ce qui a pu être construit à l'intérieur des élèves par toutes les étapes de l'activité qui est important. (F. Lombard)

*En d'autres termes... c'est le travail que vous produirez ensemble dans la mise sur pied du document qui vous sera utile à la compréhension du sujet.
*Ne perdez donc pas de temps à "formater" vos pages inutilement...

==Traitement des images==

Pour des raisons évidentes et légales, il n'est pas possible de charger nos pages Wiki avec des images.
Pourtant celles-ci sont particulièrement utiles à la bonne compréhension de certains mécanismes biologiques complexes...

Vous pouvez sans problème contourner ce problème de la manière suivante:

*dans la page Wiki, indiquez le lien de l'image si celle-ci a été prise sur Internet: ce lien permettra d'accéder à l'image "en ligne".
*copiez l'image sur le dossier Doc_annexes.doc qui se trouve sur le serveur Mimosa et renommer le fichier en indiquant le numéro de cours suivi du numéro de l'annexe:
::Exemple: '''4BIOS01_Annexe3.doc'''
*Complétez sur le document les points suivants:
:*le numéro de l'annexe
:*le titre de l'image
:*votre prénom
:*la source
:*un commentaire (légende explicative, etc.)
*Ce fichier word, sera ensuite imprimé et rajouter sous forme d'annexe au futur polycopié.
[[Utilisateur:Pierre.brawand|Pierre.brawand]] 25 septembre 2006 à 23:06 (MEST)

== Présentations orales ==
*Répartissez-vous le temps de parole entre les différents membres du groupe
*Partagez-vous les différentes parties de la présentation
*Indiquez le titre de votre présentation et son contexte (quel chapitre, ou quelle partie de chapitre, etc.)
*Exposez au préalable le plan de votre présentation: qui va parler de quoi et pourquoi!
*Description des résultats: projetez tout d'abord la page Wiki puis peut-être illustrez vos propos à l'aide d'une figure (en indiquant les sources)
*Exposez l'état de vos recherches: à l'heure actuelle de nos recherches, nous en sommes là... mais la semaine prochaine nous en serons peut-être là... Surtout, ne pas fermer les portes... il est normal que vous ne maitrisiez pas tout le sujet dès le début.
*Pour les présentations finales (qui seront généralement évaluées), prévoyez un support multimédia de type présentation Power Point avec au maximum 10 diapos. Prévoyez une diapositive d'introduction ainsi qu'une pour la conclusion.
*Faites des liens si possible avec les présentations des autres groupes
*Conclusions: la partie la plus intéressante! Elle doit permettre de soulever des questions chez vos auditeurs!
*Réponses aux questions: écoutez bien les questions... et réfléchissez quelques secondes avant de répondre. Soyez le plus clair possible dans votre réponse. Au besoin, répétez vos propos.
 
:''Site intéressant donnant des conseils pour l'élaboration du présentation orale scientifique.''
:*http://www.ipmc.cnrs.fr/~duprat/techcom/oral.htm#debut

==Elaboration des posters==
:''Quelques sites intéressants donnant des conseils pour l'élaboration des posters.''
:*http://www.ipmc.cnrs.fr/~duprat/techcom/poster.htm#conseil
:*http://mdc2007.fpms.ac.be/documents/posters.pdf
:*http://www4.utc.fr/~sp01/Fiches%20Pratiques/Consignes%20Poster.pdf

== Evaluation ==

L'évaluation portera sur différents aspects:

*Participation à la création des pages
*Connaissances acquises = tests de connaissances
*Aptitudes à transposer vos connaissances dans un situation particulière = tests d'aptitudes

*Présentations orales en classe:
**Plan de la présentation
**Clarté, concision, précision
**Vulgarisation
**Résultats
**Questions soulevées (débat)

==Rapports de laboratoire==

Quelques conseils pour l'écriture de vos rapports de biologie...
Suivez le plan suivant en indiquant les différentes rubriques

*'''Titre:'''
**Donner un titre général au laboratoire

*'''Introduction:'''
**Décrire le but de l'expérience ou de l'observation.
::*expérimentation: décrire le problème posé et résumer les travaux ou les connaissances précédents.
::*observations: décrire l'objet qui va être observé et ajouter quelques notes (provenance, mode de vie, etc…)

*'''Matériel et Méthodes:'''
**Technique utilisée
**Matériel nécessaire ou à disposition: liste précise des équipements, origine, lieu d'observation, date, météo, etc…
**Dessins et plans si nécessaire.

*'''Résultats:'''
**Penser à introduire vos résultats et à les exposer.
**Sous forme de tableaux, graphiques, dessins, avec légende ou texte explicatif.
**Vos résultats doivent être statistiquement valables… donc comparez-les à ceux de vos camarades de classe ou répéter l'expérience suffisamment de fois!
**Ne rien discuter ni commenter dans cette rubrique. Il s'agit ici uniquement de présenter les résultats.

*'''Discussion:'''
**Relier les résultats obtenus au but initial de l'expérience ou de l'observation.
**Interpréter les résultats en les reliant aux connaissances actuelles.
**Définir et proposer un éventuel modèle qui pourrait expliquer les résultats obtenus.

*'''Conclusion:'''
**Proposer d'autres expériences à faire afin de poursuivre l'étude de manière plus complète.
**Placer le travail dans un contexte plus large, discuter des conséquences, des implications, etc…
**La Conclusion peut être liée directement avec la partie Discussion sous forme de Discussion/Conclusion.

*'''Remarques:'''
**rendre un rapport propre, clair
**soigner la présentation: rapport dactylographié, entête comprenant: nom prénom, groupe, date
**résultats explicitement présentés
**textes des légendes écrits droits et reliés au dessin par un trait tiré à la règle
**dessins clairs et précis, suffisamment grands, en utilisant un bon crayon

 [[Utilisateur:Pierre.brawand|Pierre.brawand]] 19 septembre 2008 à 21:59 (MEST)

== Signatures ==
*Datez et signez vos contributions à l'aide de: <nowiki>~~~~ (4 tildes)</nowiki> que vous placerez après "lu et approuvé:"
*Ecrivez <nowiki> </nowiki> en fin de ligne pour faire un saut de ligne simple
===3BIbDF10&11===
lu et approuvé: --[[Utilisateur:Pierre.brawand|Pierre.brawand]] 2 mars 2012 à 16:17 (CET) 
lu et approuvé: --[[Utilisateur:CarolineZ|CarolineZ]] 8 mars 2012 à 09:01 (CET) 
lu et approuvé: --[[Utilisateur:MarigonaK|MarigonaK]] 8 mars 2012 à 09:25 (CET) 
lu et approuvé: --[[Utilisateur:AgnesP|AgnesP]] 9 mars 2012 à 07:05 (CET) 
lu et approuvé: [[Utilisateur:AlexanderE|AlexanderE]] 9 mars 2012 à 15:17 (CET)
lu et approuvé: --[[Utilisateur:MorganeV|MorganeV]]
lu et approuvé: 
lu et approuvé: 
lu et approuvé: 

===2BIOS01&02&03===
lu et approuvé: --[[Utilisateur:Pierre.brawand|Pierre.brawand]] 9 mars 2012 à 14:48 (CET) 
lu et approuvé: 
lu et approuvé: 
lu et approuvé: 
lu et approuvé: 
lu et approuvé: 
lu et approuvé: 
lu et approuvé: 
lu et approuvé: 
lu et approuvé: 
lu et approuvé: 
lu et approuvé: 
lu et approuvé: 
lu et approuvé: 
lu et approuvé: 

----
retour à [[Accueil]]

Sponges Cnidarians 2BIbDF09 10/11

2011-02-07T10:14:29Z

MorganeV : /* Where do Sponges live? */

=What are Sponges?=
Sponges, from the Latin pore bearers, are very primitive animals of the phylum Porifera, more precisely they are the first multicellular animals. They evolved very early from colonial protists. Their ancestors are the choanoflagellates (group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of the animals). There are between 8'000 and 9'000 species of sponges, depending of the textbook. They are '''invertebrates''', which are animals without backbones. There exist different sponges of different forms and different shapes, including tubes, fans, cups, cones, blobs, barrels, and crusts.

*see '''Appendix Sponges 1'''

==What are the main characteristics of Sponges?==
Sponges are loosely organized and lack true tissues. The body of a sponge has two outer layers separated by an acellular gel layer called the mesophyl (also called the mesenchyme). In the gel layer are either spicules (supportive needles made of calcium carbonate) or spongin fibers (a flexible skeletal material made from protein). Their sizes are from a few millimeters to more than 2 meters in diameter. They don't have any symmetry.

 The body of a sponge looks similar to a vase pierced with small holes and pores. It has thousands of pores. Sponges pump remarkable amounts of water. Water is drawn through the little pores into a central cavity, the spongocoel, then flows out the sponge through a larger opening, the osculum. In this process, they collect small particulate matter and tiny planktons, by the trapping action of the choanocytes, which are collar cells. That's why we call them filter feeders. Sponges do not have nervous, digestive or circulatory systems.

 As adults, sponges are sessile. That means that they are permanently attached to a substrate and are unable to move on their own. Most sponges are hermaphrodites (each adult can act as either the female or the male in reproduction). They produce sperm and eggs which are formed by aggregations of cells called amoebocytes in the body wall. During the proper time of the year, they release sperm cells into the sea. These cells are then captured using the same process the sponges use to capture food. The difference is that the sperm cells are moved to the "ova" of the sponge parent. And now the fertilization can take place. The eggs develop within the parent, the amount of time this takes depends on the species. When the eggs reach the "larvae" stage they are released back into the sea to seek out a place to settle and colonize.

Sponges can be either white, red, orange, green, yellow, brown, purple or black. They are known for regenerating from fragments that are broken off.. 

*see '''Appendix Sponges 2'''

==Where do Sponges live?==
Of the 9'000 or so species of sponges, only about 100 (made of spongin fiber) live in fresh water, the rest are marines. They are able to grow in most environments. Sponges can be attached to surfaces anywhere as deep as 8km in the ocean on the bottom of the ocean floor. There are a higher number of sponges in the tropics because the water is warmer. They like to live in clearer waters over murky waters formed by currents because the murky waters can clog the pores of the sponges so the sponge cannot get its nutrition and oxygen to survive.

==Why are sponges considered as animals?==
For years sponges were considered as plants, but after looking at them better, biologists decided that they have more characteristics of animals. Even sponges don’t have a definite form of symmetry, lack organs or true tissues, and are poorly organized, they are still considered as animal because of the following points. They don’t create their own food. There are considered as heterotrophes whereas plants are autotrophic orgnaisms. They have a skeleton like structure made of calcium carbonate and colalgen. They exhibit growth (basically they are born, they grow, they reproduce and then die), which is a characteristic of all animals. Their cells lack cell walls which is again a main characteristic of animal cells (plants have cellulose in their cell wall).

=What are Cnidarians?=
The name Cnidaria comes from the Greek word "cnidos" which means stinging nettle. Cnidarians (phylum Cnidaria) are mostly marine species (more than 10'000) and are the oldest of the true metazoan phyla . All the Cnidaria are aquatic and nearly all are marine. 

{{co|give a better definition of Cnidarians. Show examples? Pictures? Define their main characteristics?}}

==What are the main characteristics of Cnidarians?==
They are two different forms of Cnidarians body: '''Polypoid Shape''' or '''Medusoid Shape'''. 

'''The polypoid''' is the shape of corals and anemones. Its characteristics are the mouth and the tentacles facing up and the other side is anchored to a colony of the same aspect: for example, a coral reef. 
'''Medusoids''' are jellyfish. They are free swimmers and their tentacles and mouth are pointed down (the opposite of polypoids). 
Cnidarians have a mouth and a simple digestive system at the center of their tentacles, that is the reason why they are considered as animals and not plants. They have a radial symmetry. All cnidarians use tentacles which have stinging cells to subdue and capture food. They generally eat small planktonic animals. 

'''APPENDIX'''

=What are the four main groups of Cnidarians?=

There are '''four groups''' of Cnidarians: '''Hydrozoa, Scyphozoan, Cubozoa, and Anthozoa'''. 

'''Hydrozoans''' are in general small and colonial animals that usually exist as polyps. They live attached to rocks, sea grasses, and other solid objects, where they feed on small crustaceans and other zooplankton. There are around 2,700 described species of hydrozoans: this species have a life cycle with both polyp and medusa stages. 

'''Scyphozoans''', or jellyfish, are found in the oceans of the world and eat small planktonic animals (zooplankton) and sometimes fish. There are about 200 described species of scyphozoans, and, like hydrozoans, they have three separate life stages: a sexually produced planula stage, a strictly asexual polyp stage (usually not colonial), and a dominant, sexual, medusa stage. They can measure between a few centimeters and a meter. 

'''Cubozoans''', or box jellyfish, are a class in which the medusa is the dominant life stage. They are small, rectangular boxes (1-10 cm in length) with four tentacles (nematocyst coverded tentacles or bundless of tentacles). There are about twenty species of Cubozoans. They are fast and agile swimmers and fish on fish and crustaceans. Unlike the other Cnidarians, Cubozoans have numerous well-developed eyes along the margin of the bell which are remarkably complex because they have a cellular cornea, a lens, pigment cells and a photoreceptive, enervated retina. This eyes are used for feeding and during reproduction. Their life cycle is simila to Scyphozoans with one exception: box jellies mate. Cubozoans are highly toxic and can kill humans. 

'''Anthozoans''' have te greatest species diversity, with over 6'000 species. They have too the greatest morphological diversity, encompassing sea anemones, sea pansies, sea whips and fans, corallimorphs and soft and hard corals. The dominant life stage og Anthozoa is the polyp. It shows a greater complexity than Hydrozoans and Scyphozoans polyps. Unlike the other Cnidarians, its gut is partially subdivided by thin, folded layers of tissue taht are vertically arranged around the inside og the gut. So its medusa is completely absent. Planula develop into a reproductively capable polyp and the development can occur within the gastrovascular cavity or in the external milieu. 

*see '''Appendix Cnidarians 1'''

==How do Cnidarians reproduce?==

Cnidarians reproduce both '''asexually''' and '''sexually'''.
The reproduction is made by budding. That is a process of asexual reproduction in which a new individual develops from some generative anatomical point of the parent organism. Cnidarians have separate sexes, which specialized cells in each producing the gametes, which are excreted with the aim of meeting gametes produced by the opposite sex. When this happens a microscopic free-swimming, a larva known as a planula forms moves through the water by moving cilia that cover its body. If it survives against the predators, it eventually settles down on the sea floor and develop into polyp. After the polyp is etablished, it will reproduce by budding. These will break off and form medusoid floaters, which reproduce sexually, and begin the cycle again. This alternation of generations is unique to Cnidarians, although not all follow this pattern. 

The way of reproducing sexually is different according to the species of Cnidarians. For example for Scyphozoa (jellyfish) and Cubozoa (box jellies) a larva swims until it finds a site and then becomes a polyp. But the pricinple is the same for all. In fact, male and female produce gametes that join through external fertilization to produce polyps. 

Asexual reproduction spreads healty genotypes in huge numbers, while sexual reproduction secure genetic variation.

*see '''Appendix Cnidarians 2'''
{
{co|not enough description of the two forms of reproduction}}
[[U
tilisateur:Pierre.brawand|Pierre.brawand]] 30 janvier 2011 à 15:10 (CET)

==Where do Cnidarians live?==

They live under water. Some Cnidarians live in the oceans and seas, and a few live in freshwater. But they mostly live in saltwater or oceans.

{{co|OK... good start but you should now produce more information...}}
[[Utilisateur:Pierre.brawand|Pierre.brawand]]

{{co|Cnidarians can move. Why? Nervous system}}

{{co|Cnidarians can feed themselves actively? How? Tentacles and cnidoblasts? Also called nemotocysts}}

----
back to [[Animals_2BIbDF09_10/11]] 
back to [[Accueil]]

Sponges Cnidarians 2BIbDF09 10/11

2011-02-07T10:13:53Z

MorganeV : /* What are the main characteristics of Sponges? */

=What are Sponges?=
Sponges, from the Latin pore bearers, are very primitive animals of the phylum Porifera, more precisely they are the first multicellular animals. They evolved very early from colonial protists. Their ancestors are the choanoflagellates (group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of the animals). There are between 8'000 and 9'000 species of sponges, depending of the textbook. They are '''invertebrates''', which are animals without backbones. There exist different sponges of different forms and different shapes, including tubes, fans, cups, cones, blobs, barrels, and crusts.

*see '''Appendix Sponges 1'''

==What are the main characteristics of Sponges?==
Sponges are loosely organized and lack true tissues. The body of a sponge has two outer layers separated by an acellular gel layer called the mesophyl (also called the mesenchyme). In the gel layer are either spicules (supportive needles made of calcium carbonate) or spongin fibers (a flexible skeletal material made from protein). Their sizes are from a few millimeters to more than 2 meters in diameter. They don't have any symmetry.

 The body of a sponge looks similar to a vase pierced with small holes and pores. It has thousands of pores. Sponges pump remarkable amounts of water. Water is drawn through the little pores into a central cavity, the spongocoel, then flows out the sponge through a larger opening, the osculum. In this process, they collect small particulate matter and tiny planktons, by the trapping action of the choanocytes, which are collar cells. That's why we call them filter feeders. Sponges do not have nervous, digestive or circulatory systems.

 As adults, sponges are sessile. That means that they are permanently attached to a substrate and are unable to move on their own. Most sponges are hermaphrodites (each adult can act as either the female or the male in reproduction). They produce sperm and eggs which are formed by aggregations of cells called amoebocytes in the body wall. During the proper time of the year, they release sperm cells into the sea. These cells are then captured using the same process the sponges use to capture food. The difference is that the sperm cells are moved to the "ova" of the sponge parent. And now the fertilization can take place. The eggs develop within the parent, the amount of time this takes depends on the species. When the eggs reach the "larvae" stage they are released back into the sea to seek out a place to settle and colonize.

Sponges can be either white, red, orange, green, yellow, brown, purple or black. They are known for regenerating from fragments that are broken off.. 

*see '''Appendix Sponges 2'''

==Where do Sponges live?==
Of the 9'000 or so species of sponges, only about 100 (made of spongin fiber) live in fresh water, the rest are marines. They are able to grow in most environments. Sponges can be attached to surfaces anywhere as deep as 8km in the ocean on the bottom of the ocean floor. There are a higher number of sponges in the tropics because the water is warmer. They like to live in clearer waters over murky waters formed by currents because the murky waters can clog the pores of the sponges so the sponge cannot get its nutrition and oxygen to survive.
{{co|Could you be more precise here. Where do they live, in which oceans, at which depth, etc... etc....}}
[
[Utilisateur:Pierre.brawand|Pierre.brawand]] 30 janvier 2011 à 15:08 (CET)
{
{co|You should explain HOW do Sponges feed themselves? Why are Sponges considered as ANIMALS despite the fact that they lack some characteristics of Animals...?}}
[[
Utilisateur:Pierre.brawand|Pierre.brawand]] 30 janvier 2011 à 15:09 (CET 

==Why are sponges considered as animals?==
For years sponges were considered as plants, but after looking at them better, biologists decided that they have more characteristics of animals. Even sponges don’t have a definite form of symmetry, lack organs or true tissues, and are poorly organized, they are still considered as animal because of the following points. They don’t create their own food. There are considered as heterotrophes whereas plants are autotrophic orgnaisms. They have a skeleton like structure made of calcium carbonate and colalgen. They exhibit growth (basically they are born, they grow, they reproduce and then die), which is a characteristic of all animals. Their cells lack cell walls which is again a main characteristic of animal cells (plants have cellulose in their cell wall).

=What are Cnidarians?=
The name Cnidaria comes from the Greek word "cnidos" which means stinging nettle. Cnidarians (phylum Cnidaria) are mostly marine species (more than 10'000) and are the oldest of the true metazoan phyla . All the Cnidaria are aquatic and nearly all are marine. 

{{co|give a better definition of Cnidarians. Show examples? Pictures? Define their main characteristics?}}

==What are the main characteristics of Cnidarians?==
They are two different forms of Cnidarians body: '''Polypoid Shape''' or '''Medusoid Shape'''. 

'''The polypoid''' is the shape of corals and anemones. Its characteristics are the mouth and the tentacles facing up and the other side is anchored to a colony of the same aspect: for example, a coral reef. 
'''Medusoids''' are jellyfish. They are free swimmers and their tentacles and mouth are pointed down (the opposite of polypoids). 
Cnidarians have a mouth and a simple digestive system at the center of their tentacles, that is the reason why they are considered as animals and not plants. They have a radial symmetry. All cnidarians use tentacles which have stinging cells to subdue and capture food. They generally eat small planktonic animals. 

'''APPENDIX'''

=What are the four main groups of Cnidarians?=

There are '''four groups''' of Cnidarians: '''Hydrozoa, Scyphozoan, Cubozoa, and Anthozoa'''. 

'''Hydrozoans''' are in general small and colonial animals that usually exist as polyps. They live attached to rocks, sea grasses, and other solid objects, where they feed on small crustaceans and other zooplankton. There are around 2,700 described species of hydrozoans: this species have a life cycle with both polyp and medusa stages. 

'''Scyphozoans''', or jellyfish, are found in the oceans of the world and eat small planktonic animals (zooplankton) and sometimes fish. There are about 200 described species of scyphozoans, and, like hydrozoans, they have three separate life stages: a sexually produced planula stage, a strictly asexual polyp stage (usually not colonial), and a dominant, sexual, medusa stage. They can measure between a few centimeters and a meter. 

'''Cubozoans''', or box jellyfish, are a class in which the medusa is the dominant life stage. They are small, rectangular boxes (1-10 cm in length) with four tentacles (nematocyst coverded tentacles or bundless of tentacles). There are about twenty species of Cubozoans. They are fast and agile swimmers and fish on fish and crustaceans. Unlike the other Cnidarians, Cubozoans have numerous well-developed eyes along the margin of the bell which are remarkably complex because they have a cellular cornea, a lens, pigment cells and a photoreceptive, enervated retina. This eyes are used for feeding and during reproduction. Their life cycle is simila to Scyphozoans with one exception: box jellies mate. Cubozoans are highly toxic and can kill humans. 

'''Anthozoans''' have te greatest species diversity, with over 6'000 species. They have too the greatest morphological diversity, encompassing sea anemones, sea pansies, sea whips and fans, corallimorphs and soft and hard corals. The dominant life stage og Anthozoa is the polyp. It shows a greater complexity than Hydrozoans and Scyphozoans polyps. Unlike the other Cnidarians, its gut is partially subdivided by thin, folded layers of tissue taht are vertically arranged around the inside og the gut. So its medusa is completely absent. Planula develop into a reproductively capable polyp and the development can occur within the gastrovascular cavity or in the external milieu. 

*see '''Appendix Cnidarians 1'''

==How do Cnidarians reproduce?==

Cnidarians reproduce both '''asexually''' and '''sexually'''.
The reproduction is made by budding. That is a process of asexual reproduction in which a new individual develops from some generative anatomical point of the parent organism. Cnidarians have separate sexes, which specialized cells in each producing the gametes, which are excreted with the aim of meeting gametes produced by the opposite sex. When this happens a microscopic free-swimming, a larva known as a planula forms moves through the water by moving cilia that cover its body. If it survives against the predators, it eventually settles down on the sea floor and develop into polyp. After the polyp is etablished, it will reproduce by budding. These will break off and form medusoid floaters, which reproduce sexually, and begin the cycle again. This alternation of generations is unique to Cnidarians, although not all follow this pattern. 

The way of reproducing sexually is different according to the species of Cnidarians. For example for Scyphozoa (jellyfish) and Cubozoa (box jellies) a larva swims until it finds a site and then becomes a polyp. But the pricinple is the same for all. In fact, male and female produce gametes that join through external fertilization to produce polyps. 

Asexual reproduction spreads healty genotypes in huge numbers, while sexual reproduction secure genetic variation.

*see '''Appendix Cnidarians 2'''
{
{co|not enough description of the two forms of reproduction}}
[[U
tilisateur:Pierre.brawand|Pierre.brawand]] 30 janvier 2011 à 15:10 (CET)

==Where do Cnidarians live?==

They live under water. Some Cnidarians live in the oceans and seas, and a few live in freshwater. But they mostly live in saltwater or oceans.

{{co|OK... good start but you should now produce more information...}}
[[Utilisateur:Pierre.brawand|Pierre.brawand]]

{{co|Cnidarians can move. Why? Nervous system}}

{{co|Cnidarians can feed themselves actively? How? Tentacles and cnidoblasts? Also called nemotocysts}}

----
back to [[Animals_2BIbDF09_10/11]] 
back to [[Accueil]]

Sponges Cnidarians 2BIbDF09 10/11

2011-02-07T10:13:28Z

MorganeV : /* What are the main characteristics of Sponges? */

=What are Sponges?=
Sponges, from the Latin pore bearers, are very primitive animals of the phylum Porifera, more precisely they are the first multicellular animals. They evolved very early from colonial protists. Their ancestors are the choanoflagellates (group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of the animals). There are between 8'000 and 9'000 species of sponges, depending of the textbook. They are '''invertebrates''', which are animals without backbones. There exist different sponges of different forms and different shapes, including tubes, fans, cups, cones, blobs, barrels, and crusts.

*see '''Appendix Sponges 1'''

==What are the main characteristics of Sponges?==
Sponges are loosely organized and lack true tissues. The body of a sponge has two outer layers separated by an acellular gel layer called the mesophyl (also called the mesenchyme). In the gel layer are either spicules (supportive needles made of calcium carbonate) or spongin fibers (a flexible skeletal material made from protein). Their sizes are from a few millimeters to more than 2 meters in diameter. They don't have any symmetry.

 The body of a sponge looks similar to a vase pierced with small holes and pores. It has thousands of pores. Sponges pump remarkable amounts of water. Water is drawn through the little pores into a central cavity, the spongocoel, then flows out the sponge through a larger opening, the osculum. In this process, they collect small particulate matter and tiny planktons, by the trapping action of the choanocytes, which are collar cells. That's why we call them filter feeders. Sponges do not have nervous, digestive or circulatory systems.

 As adults, sponges are sessile. That means that they are permanently attached to a substrate and are unable to move on their own. Most sponges are hermaphrodites (each adult can act as either the female or the male in reproduction). They produce sperm and eggs which are formed by aggregations of cells called amoebocytes in the body wall. During the proper time of the year, they release sperm cells into the sea. These cells are then captured using the same process the sponges use to capture food. The difference is that the sperm cells are moved to the "ova" of the sponge parent. And now the fertilization can take place. The eggs develop within the parent, the amount of time this takes depends on the species. When the eggs reach the "larvae" stage they are released back into the sea to seek out a place to settle and colonize.

Sponges can be either white, red, orange, green, yellow, brown, purple or black. They are known for regenerating from fragments that are broken off.. 

*see '''Appendix Sponges 2'''
{{co|good. Maybe you could create an Appendix document showing the main characteristics of Sponges}}
[
[Utilisateur:Pierre.brawand|Pierre.brawand]]

==Where do Sponges live?==
Of the 9'000 or so species of sponges, only about 100 (made of spongin fiber) live in fresh water, the rest are marines. They are able to grow in most environments. Sponges can be attached to surfaces anywhere as deep as 8km in the ocean on the bottom of the ocean floor. There are a higher number of sponges in the tropics because the water is warmer. They like to live in clearer waters over murky waters formed by currents because the murky waters can clog the pores of the sponges so the sponge cannot get its nutrition and oxygen to survive.
{{co|Could you be more precise here. Where do they live, in which oceans, at which depth, etc... etc....}}
[
[Utilisateur:Pierre.brawand|Pierre.brawand]] 30 janvier 2011 à 15:08 (CET)
{
{co|You should explain HOW do Sponges feed themselves? Why are Sponges considered as ANIMALS despite the fact that they lack some characteristics of Animals...?}}
[[
Utilisateur:Pierre.brawand|Pierre.brawand]] 30 janvier 2011 à 15:09 (CET 

==Why are sponges considered as animals?==
For years sponges were considered as plants, but after looking at them better, biologists decided that they have more characteristics of animals. Even sponges don’t have a definite form of symmetry, lack organs or true tissues, and are poorly organized, they are still considered as animal because of the following points. They don’t create their own food. There are considered as heterotrophes whereas plants are autotrophic orgnaisms. They have a skeleton like structure made of calcium carbonate and colalgen. They exhibit growth (basically they are born, they grow, they reproduce and then die), which is a characteristic of all animals. Their cells lack cell walls which is again a main characteristic of animal cells (plants have cellulose in their cell wall).

=What are Cnidarians?=
The name Cnidaria comes from the Greek word "cnidos" which means stinging nettle. Cnidarians (phylum Cnidaria) are mostly marine species (more than 10'000) and are the oldest of the true metazoan phyla . All the Cnidaria are aquatic and nearly all are marine. 

{{co|give a better definition of Cnidarians. Show examples? Pictures? Define their main characteristics?}}

==What are the main characteristics of Cnidarians?==
They are two different forms of Cnidarians body: '''Polypoid Shape''' or '''Medusoid Shape'''. 

'''The polypoid''' is the shape of corals and anemones. Its characteristics are the mouth and the tentacles facing up and the other side is anchored to a colony of the same aspect: for example, a coral reef. 
'''Medusoids''' are jellyfish. They are free swimmers and their tentacles and mouth are pointed down (the opposite of polypoids). 
Cnidarians have a mouth and a simple digestive system at the center of their tentacles, that is the reason why they are considered as animals and not plants. They have a radial symmetry. All cnidarians use tentacles which have stinging cells to subdue and capture food. They generally eat small planktonic animals. 

'''APPENDIX'''

=What are the four main groups of Cnidarians?=

There are '''four groups''' of Cnidarians: '''Hydrozoa, Scyphozoan, Cubozoa, and Anthozoa'''. 

'''Hydrozoans''' are in general small and colonial animals that usually exist as polyps. They live attached to rocks, sea grasses, and other solid objects, where they feed on small crustaceans and other zooplankton. There are around 2,700 described species of hydrozoans: this species have a life cycle with both polyp and medusa stages. 

'''Scyphozoans''', or jellyfish, are found in the oceans of the world and eat small planktonic animals (zooplankton) and sometimes fish. There are about 200 described species of scyphozoans, and, like hydrozoans, they have three separate life stages: a sexually produced planula stage, a strictly asexual polyp stage (usually not colonial), and a dominant, sexual, medusa stage. They can measure between a few centimeters and a meter. 

'''Cubozoans''', or box jellyfish, are a class in which the medusa is the dominant life stage. They are small, rectangular boxes (1-10 cm in length) with four tentacles (nematocyst coverded tentacles or bundless of tentacles). There are about twenty species of Cubozoans. They are fast and agile swimmers and fish on fish and crustaceans. Unlike the other Cnidarians, Cubozoans have numerous well-developed eyes along the margin of the bell which are remarkably complex because they have a cellular cornea, a lens, pigment cells and a photoreceptive, enervated retina. This eyes are used for feeding and during reproduction. Their life cycle is simila to Scyphozoans with one exception: box jellies mate. Cubozoans are highly toxic and can kill humans. 

'''Anthozoans''' have te greatest species diversity, with over 6'000 species. They have too the greatest morphological diversity, encompassing sea anemones, sea pansies, sea whips and fans, corallimorphs and soft and hard corals. The dominant life stage og Anthozoa is the polyp. It shows a greater complexity than Hydrozoans and Scyphozoans polyps. Unlike the other Cnidarians, its gut is partially subdivided by thin, folded layers of tissue taht are vertically arranged around the inside og the gut. So its medusa is completely absent. Planula develop into a reproductively capable polyp and the development can occur within the gastrovascular cavity or in the external milieu. 

*see '''Appendix Cnidarians 1'''

==How do Cnidarians reproduce?==

Cnidarians reproduce both '''asexually''' and '''sexually'''.
The reproduction is made by budding. That is a process of asexual reproduction in which a new individual develops from some generative anatomical point of the parent organism. Cnidarians have separate sexes, which specialized cells in each producing the gametes, which are excreted with the aim of meeting gametes produced by the opposite sex. When this happens a microscopic free-swimming, a larva known as a planula forms moves through the water by moving cilia that cover its body. If it survives against the predators, it eventually settles down on the sea floor and develop into polyp. After the polyp is etablished, it will reproduce by budding. These will break off and form medusoid floaters, which reproduce sexually, and begin the cycle again. This alternation of generations is unique to Cnidarians, although not all follow this pattern. 

The way of reproducing sexually is different according to the species of Cnidarians. For example for Scyphozoa (jellyfish) and Cubozoa (box jellies) a larva swims until it finds a site and then becomes a polyp. But the pricinple is the same for all. In fact, male and female produce gametes that join through external fertilization to produce polyps. 

Asexual reproduction spreads healty genotypes in huge numbers, while sexual reproduction secure genetic variation.

*see '''Appendix Cnidarians 2'''
{
{co|not enough description of the two forms of reproduction}}
[[U
tilisateur:Pierre.brawand|Pierre.brawand]] 30 janvier 2011 à 15:10 (CET)

==Where do Cnidarians live?==

They live under water. Some Cnidarians live in the oceans and seas, and a few live in freshwater. But they mostly live in saltwater or oceans.

{{co|OK... good start but you should now produce more information...}}
[[Utilisateur:Pierre.brawand|Pierre.brawand]]

{{co|Cnidarians can move. Why? Nervous system}}

{{co|Cnidarians can feed themselves actively? How? Tentacles and cnidoblasts? Also called nemotocysts}}

----
back to [[Animals_2BIbDF09_10/11]] 
back to [[Accueil]]

Sponges Cnidarians 2BIbDF09 10/11

2011-02-06T10:25:08Z

MorganeV : /* What are Sponges? */

=What are Sponges?=
Sponges, from the Latin pore bearers, are very primitive animals of the phylum Porifera, more precisely they are the first multicellular animals. They evolved very early from colonial protists. Their ancestors are the choanoflagellates (group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of the animals). There are between 8'000 and 9'000 species of sponges, depending of the textbook. They are '''invertebrates''', which are animals without backbones. There exist different sponges of different forms and different shapes, including tubes, fans, cups, cones, blobs, barrels, and crusts.

*see '''Appendix Sponges 1'''

==What are the main characteristics of Sponges?==
Sponges are loosely organized and lack true tissues. The body of a sponge has two outer layers separated by an acellular gel layer called the mesophyl (also called the mesenchyme). In the gel layer are either spicules (supportive needles made of calcium carbonate) or spongin fibers (a flexible skeletal material made from protein). Their sizes are from a few millimeters to more than 2 meters in diameter. They don't have any symmetry.

 The body of a sponge looks similar to a vase pierced with small holes and pores. It has thousands of pores. Water is drawn through the little pores into a central cavity, the spongocoel, then flows out the sponge through a larger opening, the osculum. In this process, they collect small particulate matter and tiny planktons, by the trapping action of the choanocytes, which are collar cells. That's why we call them filter feeders. Sponges do not have nervous, digestive or circulatory systems.

 As adults, sponges are sessile. That means that they are permanently attached to a substrate and are unable to move on their own. Most sponges are hermaphrodites (each adult can act as either the female or the male in reproduction). They produce sperm and eggs which are formed by aggregations of cells called amoebocytes in the body wall. During the proper time of the year, they release sperm cells into the sea. These cells are then captured using the same process the sponges use to capture food. The difference is that the sperm cells are moved to the "ova" of the sponge parent. And now the fertilization can take place. The eggs develop within the parent, the amount of time this takes depends on the species. When the eggs reach the "larvae" stage they are released back into the sea to seek out a place to settle and colonize.

Sponges can be either white, red, orange, green, yellow, brown, purple or black. They are known for regenerating from fragments that are broken off.. 

*see '''Appendix Sponges 2'''
{{co|good. Maybe you could create an Appendix document showing the main characteristics of Sponges}}
[
[Utilisateur:Pierre.brawand|Pierre.brawand]]

==Where do Sponges live?==
Of the 9'000 or so species of sponges, only about 100 (made of spongin fiber) live in fresh water, the rest are marines. They are able to grow in most environments. Sponges can be attached to surfaces anywhere as deep as 8km in the ocean on the bottom of the ocean floor. There are a higher number of sponges in the tropics because the water is warmer. They like to live in clearer waters over murky waters formed by currents because the murky waters can clog the pores of the sponges so the sponge cannot get its nutrition and oxygen to survive.
{{co|Could you be more precise here. Where do they live, in which oceans, at which depth, etc... etc....}}
[
[Utilisateur:Pierre.brawand|Pierre.brawand]] 30 janvier 2011 à 15:08 (CET)
{
{co|You should explain HOW do Sponges feed themselves? Why are Sponges considered as ANIMALS despite the fact that they lack some characteristics of Animals...?}}
[[
Utilisateur:Pierre.brawand|Pierre.brawand]] 30 janvier 2011 à 15:09 (CET 

==Why are sponges considered as animals?==
For years sponges were considered as plants, but after looking at them better, biologists decided that they have more caracteristics of animals. Even sponges don’t have a definite form of symmetry, lack organs or true tissues, and are poorly organized, they are considered as animal. They are considered as animals because they have the characteristics of life. They don’t create their own food so they are not plants: they are filter feeders. They have a skeleton like structure made of calcium carbonate. They exhibit growth (basically they are born, they grow, they reproduce and then die), which is a characteristic of all animals.

=What are Cnidarians?=
The name Cnidaria comes from the Greek word "cnidos" which means stinging nettle. Cnidarians (phylum Cnidaria) are mostly marine species (more than 10'000) and are the oldest of the true metazoan phyla . All the Cnidaria are aquatic and nearly all are marine. There are '''four groups''' of Cnidarians: '''Hydrozoa, Scyphozoan, Cubozoa, and Anthozoa'''. 

'''Hydrozoans''' are in general small and colonial animals that usually exist as polyps. They live attached to rocks, sea grasses, and other solid objects, where they feed on small crustaceans and other zooplankton. There are around 2,700 described species of hydrozoans: this species have a life cycle with both polyp and medusa stages. 

'''Scyphozoans''', or jellyfish, are found in the oceans of the world and eat small planktonic animals (zooplankton) and sometimes fish. There are about 200 described species of scyphozoans, and, like hydrozoans, they have three separate life stages: a sexually produced planula stage, a strictly asexual polyp stage (usually not colonial), and a dominant, sexual, medusa stage. They can measure between a few centimeters and a meter. 

'''Cubozoans''', or box jellyfish, are a class in which the medusa is the dominant life stage. They are small, rectangular boxes (1-10 cm in length) with four tentacles (nematocyst coverded tentacles or bundless of tentacles). There are about twenty species of Cubozoans. They are fast and agile swimmers and fish on fish and crustaceans. Unlike the other Cnidarians, Cubozoans have numerous well-developed eyes along the margin of the bell which are remarkably complex because they have a cellular cornea, a lens, pigment cells and a photoreceptive, enervated retina. This eyes are used for feeding and during reproduction. Their life cycle is simila to Scyphozoans with one exception: box jellies mate. Cubozoans are highly toxic and can kill humans. 

'''Anthozoans''' have te greatest species diversity, with over 6'000 species. They have too the greatest morphological diversity, encompassing sea anemones, sea pansies, sea whips and fans, corallimorphs and soft and hard corals. The dominant life stage og Anthozoa is the polyp. It shows a greater complexity than Hydrozoans and Scyphozoans polyps. Unlike the other Cnidarians, its gut is partially subdivided by thin, folded layers of tissue taht are vertically arranged around the inside og the gut. So its medusa is completely absent. Planula develop into a reproductively capable polyp and the development can occur within the gastrovascular cavity or in the external milieu. 

*see '''Appendix Cnidarians 1'''

==What are the main characteristics of Cnidarians?==
They are two different forms of Cnidarians body: '''Polypoid Shape''' or '''Medusoid Shape'''. 

'''The polypoid''' is the shape of corals and anemones. Its characteristics are the mouth and the tentacles facing up and the other side is anchored to a colony of the same aspect: for example, a coral reef. 
'''Medusoids''' are jellyfish. They are free swimmers and their tentacles and mouth are pointed down (the opposite of polypoids). 
Cnidarians have a mouth and a simple digestive system at the center of their tentacles, that is the reason why they are considered as animals and not plants. They have a radial symmetry. All cnidarians use tentacles which have stinging cells to subdue and capture food. They generally eat small planktonic animals. 

Cnidarians reproduce both '''asexually''' and '''sexually'''.
The reproduction is made by budding. That is a process of asexual reproduction in which a new individual develops from some generative anatomical point of the parent organism. 

The way of reproducing sexually is different according to the species of Cnidarians. For example for Scyphozoa (jellyfish) and Cubozoa (box jellies) a larva swims until it finds a site and then becomes a polyp. But the pricinple is the same for all. In fact, male and female produce gametes that join through external fertilization to produce polyps. 

Asexual reproduction spreads healty genotypes in huge numbers, while sexual reproduction secure genetic variation.

*see '''Appendix Cnidarians 2'''
{{co|not enough description of the two forms of reproduction}}
[[U
tilisateur:Pierre.brawand|Pierre.brawand]] 30 janvier 2011 à 15:10 (CET)

==Where do Cnidarians live?==

They live under water. Some Cnidarians live in the oceans and seas, and a few live in freshwater. But they mostly live in saltwater or oceans.

{{co|OK... good start but you should now produce more information...}}
[[
U
tilisateur:Pierre.brawand|Pierre.brawand]]

----
back to [[Animals_2BIbDF09_10/11]] 
back to [[Accueil]]

Sponges Cnidarians 2BIbDF09 10/11

2011-01-31T09:54:28Z

MorganeV : /* What are Sponges? */

=What are Sponges?=
Sponges, from the Latin pore bearers, are very primitive animals of the phylum Porifera, more precisely they are the first multicellular animals. They evolved very early from colonial protists. Their ancestors are the choanoflagellates (group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of the animals). There are between 8'000 and 9'000 species of sponges, depending of the textbook. They are '''invertebrates''', which are animals without backbones. There exist different sponges of different forms and different shapes, including tubes, fans, cups, cones, blobs, barrels, and crusts.

*see '''Appendix Sponges 1'''

==What are the main characteristics of Sponges?==
Sponges are loosely organized and lack true tissues. The body of a sponge has two outer layers separated by an acellular gel layer called the mesophyl (also called the mesenchyme). In the gel layer are either spicules (supportive needles made of calcium carbonate) or spongin fibers (a flexible skeletal material made from protein). Their sizes are from a few millimeters to more than 2 meters in diameter. They don't have any symmetry.

 The body of a sponge looks similar to a vase pierced with small holes and pores. It has thousands of pores. Water is drawn through the little pores into a central cavity, the spongocoel, then flows out the sponge through a larger opening, the osculum. In this process, they collect small particulate matter and tiny planktons, by the trapping action of the choanocytes, which are collar cells. That's why we call them filter feeders. Sponges do not have nervous, digestive or circulatory systems.

 As adults, sponges are sessile. That means that they are permanently attached to a substrate and are unable to move on their own. Most sponges are hermaphrodites (each adult can act as either the female or the male in reproduction). They produce sperm and eggs which are formed by aggregations of cells called amoebocytes in the body wall. During the proper time of the year, they release sperm cells into the sea. These cells are then captured using the same process the sponges use to capture food. The difference is that the sperm cells are moved to the "ova" of the sponge parent. And now the fertilization can take place. The eggs develop within the parent, the amount of time this takes depends on the species. When the eggs reach the "larvae" stage they are released back into the sea to seek out a place to settle and colonize.

Sponges can be either white, red, orange, green, yellow, brown, purple or black. They are known for regenerating from fragments that are broken off.. 

*see '''Appendix Sponges 2'''
{{co|good. Maybe you could create an Appendix document showing the main characteristics of Sponges}}
[
[Utilisateur:Pierre.brawand|Pierre.brawand]]

==Where do Sponges live?==
Of the 9'000 or so species of sponges, only about 100 (made of spongin fiber) live in fresh water, the rest are marines. They are able to grow in most environments. Sponges can be attached to surfaces anywhere as deep as 8km in the ocean on the bottom of the ocean floor. There are a higher number of sponges in the tropics because the water is warmer. They like to live in clearer waters over murky waters formed by currents because the murky waters can clog the pores of the sponges so the sponge cannot get its nutrition and oxygen to survive.
{{co|Could you be more precise here. Where do they live, in which oceans, at which depth, etc... etc....}}[
[Utilisateur:Pierre.brawand|Pierre.brawand]] 30 janvier 2011 à 15:08 (CET)
{
{co|You should explain HOW do Sponges feed themselves? Why are Sponges considered as ANIMALS despite the fact that they lack some characteristics of Animals...?}}
[[
Utilisateur:Pierre.brawand|Pierre.brawand]] 30 janvier 2011 à 15:09 (CET 

==Why are sponges considered as animals?==

=What are Cnidarians?=
The name Cnidaria comes from the Greek word "cnidos" which means stinging nettle. Cnidarians (phylum Cnidaria) are mostly marine species (more than 10'000) and are the oldest of the true metazoan phyla . All the Cnidaria are aquatic and nearly all are marine. There are '''four groups''' of Cnidarians: '''Hydrozoa, Scyphozoan, Cubozoa, and Anthozoa'''. 

'''Hydrozoans''' are in general small and colonial animals that usually exist as polyps. They live attached to rocks, sea grasses, and other solid objects, where they feed on small crustaceans and other zooplankton. There are around 2,700 described species of hydrozoans: this species have a life cycle with both polyp and medusa stages. 

'''Scyphozoans''', or jellyfish, are found in the oceans of the world and eat small planktonic animals (zooplankton) and sometimes fish. There are about 200 described species of scyphozoans, and, like hydrozoans, they have three separate life stages: a sexually produced planula stage, a strictly asexual polyp stage (usually not colonial), and a dominant, sexual, medusa stage. They can measure between a few centimeters and a meter. 

'''Cubozoans''', or box jellyfish, are a class in which the medusa is the dominant life stage. They are small, rectangular boxes (1-10 cm in length) with four tentacles (nematocyst coverded tentacles or bundless of tentacles). There are about twenty species of Cubozoans. They are fast and agile swimmers and fish on fish and crustaceans. Unlike the other Cnidarians, Cubozoans have numerous well-developed eyes along the margin of the bell which are remarkably complex because they have a cellular cornea, a lens, pigment cells and a photoreceptive, enervated retina. This eyes are used for feeding and during reproduction. Their life cycle is simila to Scyphozoans with one exception: box jellies mate. Cubozoans are highly toxic and can kill humans. 

'''Anthozoans''' have te greatest species diversity, with over 6'000 species. They have too the greatest morphological diversity, encompassing sea anemones, sea pansies, sea whips and fans, corallimorphs and soft and hard corals. The dominant life stage og Anthozoa is the polyp. It shows a greater complexity than Hydrozoans and Scyphozoans polyps. Unlike the other Cnidarians, its gut is partially subdivided by thin, folded layers of tissue taht are vertically arranged around the inside og the gut. So its medusa is completely absent. Planula develop into a reproductively capable polyp and the development can occur within the gastrovascular cavity or in the external milieu. 

*see '''Appendix Cnidarians 1'''

==What are the main characteristics of Cnidarians?==
They are two different forms of Cnidarians body: '''Polypoid Shape''' or '''Medusoid Shape'''. 

'''The polypoid''' is the shape of corals and anemones. Its characteristics are the mouth and the tentacles facing up and the other side is anchored to a colony of the same aspect: for example, a coral reef. 
'''Medusoids''' are jellyfish. They are free swimmers and their tentacles and mouth are pointed down (the opposite of polypoids). 
Cnidarians have a mouth and a simple digestive system at the center of their tentacles, that is the reason why they are considered as animals and not plants. They have a radial symmetry. All cnidarians use tentacles which have stinging cells to subdue and capture food. They generally eat small planktonic animals.

 Cnidarians reproduce both '''asexually''' and '''sexually'''.
The reproduction is made by budding. That is a process of asexual reproduction in which a new individual develops from some generative anatomical point of the parent organism. 

*see '''Appendix Cnidarians 1'''
{{co|not enough description of the two forms of reproduction}}
[
[U
tilisateur:Pierre.brawand|Pierre.brawand]] 30 janvier 2011 à 15:10 (CET)

==Where do Cnidarians live?==

They live under water. Some Cnidarians live in the oceans and seas, and a few live in freshwater. But they mostly live in saltwater or oceans.

{{co|OK... good start but you should now produce more information...}}
[[
U
tilisateur:Pierre.brawand|Pierre.brawand]]

----
back to [[Animals_2BIbDF09_10/11]] 
back to [[Accueil]]

Sponges Cnidarians 2BIbDF09 10/11

2011-01-31T09:48:12Z

MorganeV : /* Where do Sponges live? */

=What are Sponges?=
Sponges, from the Latin pore bearers, are very primitive animals of the phylum Porifera, more precisely they are the first multicellular animals. They evolved very early from colonial protists. Their ancestors are the choanoflagellates (group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of the animals). There are between 8'000 and 9'000 species of sponges, depending of the textbook. They are '''invertebrates''', which are animals without backbones. There exist different sponges of different forms and different shapes, including tubes, fans, cups, cones, blobs, barrels, and crusts.

*see '''Appendix Sponges 1'''

==What are the main characteristics of Sponges?==
Sponges are loosely organized and lack true tissues. The body of a sponge has two outer layers separated by an acellular gel layer called the mesophyl (also called the mesenchyme). In the gel layer are either spicules (supportive needles made of calcium carbonate) or spongin fibers (a flexible skeletal material made from protein). Their sizes are from a few millimeters to more than 2 meters in diameter. They don't have any symmetry.

 The body of a sponge looks similar to a vase pierced with small holes and pores. It has thousands of pores. Water is drawn through the little pores into a central cavity, the spongocoel, then flows out the sponge through a larger opening, the osculum. In this process, they collect small particulate matter and tiny planktons, by the trapping action of the choanocytes, which are collar cells. That's why we call them filter feeders. Sponges do not have nervous, digestive or circulatory systems.

 As adults, sponges are sessile. That means that they are permanently attached to a substrate and are unable to move on their own. Most sponges are hermaphrodites (each adult can act as either the female or the male in reproduction). They produce sperm and eggs which are formed by aggregations of cells called amoebocytes in the body wall. During the proper time of the year, they release sperm cells into the sea. These cells are then captured using the same process the sponges use to capture food. The difference is that the sperm cells are moved to the "ova" of the sponge parent. And now the fertilization can take place. The eggs develop within the parent, the amount of time this takes depends on the species. When the eggs reach the "larvae" stage they are released back into the sea to seek out a place to settle and colonize.

Sponges can be either white, red, orange, green, yellow, brown, purple or black. They are known for regenerating from fragments that are broken off.. 

*see '''Appendix Sponges 2'''
{{co|good. Maybe you could create an Appendix document showing the main characteristics of Sponges}}
[
[Utilisateur:Pierre.brawand|Pierre.brawand]]

==Where do Sponges live?==
Of the 9'000 or so species of sponges, only about 100 (made of spongin fiber) live in fresh water, the rest are marines. They are able to grow in most environments. Sponges can be attached to surfaces anywhere as deep as 8km in the ocean on the bottom of the ocean floor. There are a higher number of sponges in the tropics because the water is warmer. They like to live in clearer waters over murky waters formed by currents because the murky waters can clog the pores of the sponges so the sponge cannot get its nutrition and oxygen to survive.
{{co|Could you be more precise here. Where do they live, in which oceans, at which depth, etc... etc....}}
[
[Utilisateur:Pierre.brawand|Pierre.brawand]] 30 janvier 2011 à 15:08 (CET)
{
{co|You should explain HOW do Sponges feed themselves? Why are Sponges considered as ANIMALS despite the fact that they lack some characteristics of Animals...?}}
[[
Utilisateur:Pierre.brawand|Pierre.brawand]] 30 janvier 2011 à 15:09 (CET)

=What are Cnidarians?=
The name Cnidaria comes from the Greek word "cnidos" which means stinging nettle. Cnidarians (phylum Cnidaria) are mostly marine species (more than 10'000) and are the oldest of the true metazoan phyla . All the Cnidaria are aquatic and nearly all are marine. There are '''four groups''' of Cnidarians: '''Hydrozoa, Scyphozoan, Cubozoa, and Anthozoa'''. 

'''Hydrozoans''' are in general small and colonial animals that usually exist as polyps. They live attached to rocks, sea grasses, and other solid objects, where they feed on small crustaceans and other zooplankton. There are around 2,700 described species of hydrozoans: this species have a life cycle with both polyp and medusa stages. 

'''Scyphozoans''', or jellyfish, are found in the oceans of the world and eat small planktonic animals (zooplankton) and sometimes fish. There are about 200 described species of scyphozoans, and, like hydrozoans, they have three separate life stages: a sexually produced planula stage, a strictly asexual polyp stage (usually not colonial), and a dominant, sexual, medusa stage. They can measure between a few centimeters and a meter. 

'''Cubozoans''', or box jellyfish, are a class in which the medusa is the dominant life stage. They are small, rectangular boxes (1-10 cm in length) with four tentacles (nematocyst coverded tentacles or bundless of tentacles). There are about twenty species of Cubozoans. They are fast and agile swimmers and fish on fish and crustaceans. Unlike the other Cnidarians, Cubozoans have numerous well-developed eyes along the margin of the bell which are remarkably complex because they have a cellular cornea, a lens, pigment cells and a photoreceptive, enervated retina. This eyes are used for feeding and during reproduction. Their life cycle is simila to Scyphozoans with one exception: box jellies mate. Cubozoans are highly toxic and can kill humans. 

'''Anthozoans''' have te greatest species diversity, with over 6'000 species. They have too the greatest morphological diversity, encompassing sea anemones, sea pansies, sea whips and fans, corallimorphs and soft and hard corals. The dominant life stage og Anthozoa is the polyp. It shows a greater complexity than Hydrozoans and Scyphozoans polyps. Unlike the other Cnidarians, its gut is partially subdivided by thin, folded layers of tissue taht are vertically arranged around the inside og the gut. So its medusa is completely absent. Planula develop into a reproductively capable polyp and the development can occur within the gastrovascular cavity or in the external milieu. 

*see '''Appendix Cnidarians 1'''

==What are the main characteristics of Cnidarians?==
They are two different forms of Cnidarians body: '''Polypoid Shape''' or '''Medusoid Shape'''. 

'''The polypoid''' is the shape of corals and anemones. Its characteristics are the mouth and the tentacles facing up and the other side is anchored to a colony of the same aspect: for example, a coral reef. 
'''Medusoids''' are jellyfish. They are free swimmers and their tentacles and mouth are pointed down (the opposite of polypoids). 
Cnidarians have a mouth and a simple digestive system at the center of their tentacles, that is the reason why they are considered as animals and not plants. They have a radial symmetry. All cnidarians use tentacles which have stinging cells to subdue and capture food. They generally eat small planktonic animals.

 Cnidarians reproduce both '''asexually''' and '''sexually'''.
The reproduction is made by budding. That is a process of asexual reproduction in which a new individual develops from some generative anatomical point of the parent organism. 

*see '''Appendix Cnidarians 1'''
{{co|not enough description of the two forms of reproduction}}
[
[U
tilisateur:Pierre.brawand|Pierre.brawand]] 30 janvier 2011 à 15:10 (CET)

==Where do Cnidarians live?==

They live under water. Some Cnidarians live in the oceans and seas, and a few live in freshwater. But they mostly live in saltwater or oceans.

{{co|OK... good start but you should now produce more information...}}
[[
U
tilisateur:Pierre.brawand|Pierre.brawand]]

----
back to [[Animals_2BIbDF09_10/11]] 
back to [[Accueil]]

Sponges Cnidarians 2BIbDF09 10/11

2011-01-31T09:13:24Z

MorganeV : /* What are Sponges? */

=What are Sponges?=
Sponges, from the Latin pore bearers, are very primitive animals of the phylum Porifera, more precisely they are the first multicellular animals. They evolved very early from colonial protists. Their ancestors are the choanoflagellates (group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of the animals). There are between 8'000 and 9'000 species of sponges, depending of the textbook. They are '''invertebrates''', which are animals without backbones. There exist different sponges of different forms and different shapes, including tubes, fans, cups, cones, blobs, barrels, and crusts.

*see '''Appendix Sponges 1'''

==What are the main characteristics of Sponges?==
Sponges are loosely organized and lack true tissues. The body of a sponge has two outer layers separated by an acellular gel layer called the mesophyl (also called the mesenchyme). In the gel layer are either spicules (supportive needles made of calcium carbonate) or spongin fibers (a flexible skeletal material made from protein). Their sizes are from a few millimeters to more than 2 meters in diameter. They don't have any symmetry.

 The body of a sponge looks similar to a vase pierced with small holes and pores. It has thousands of pores. Water is drawn through the little pores into a central cavity, the spongocoel, then flows out the sponge through a larger opening, the osculum. In this process, they collect small particulate matter and tiny planktons, by the trapping action of the choanocytes, which are collar cells. That's why we call them filter feeders. Sponges do not have nervous, digestive or circulatory systems.

 As adults, sponges are sessile. That means that they are permanently attached to a substrate and are unable to move on their own. Most sponges are hermaphrodites (each adult can act as either the female or the male in reproduction). They produce sperm and eggs which are formed by aggregations of cells called amoebocytes in the body wall. During the proper time of the year, they release sperm cells into the sea. These cells are then captured using the same process the sponges use to capture food. The difference is that the sperm cells are moved to the "ova" of the sponge parent. And now the fertilization can take place. The eggs develop within the parent, the amount of time this takes depends on the species. When the eggs reach the "larvae" stage they are released back into the sea to seek out a place to settle and colonize.

Sponges can be either white, red, orange, green, yellow, brown, purple or black. They are known for regenerating from fragments that are broken off.. 

*see '''Appendix Sponges 2'''
{{co|good. Maybe you could create an Appendix document showing the main characteristics of Sponges}}
[
[Utilisateur:Pierre.brawand|Pierre.brawand]]

==Where do Sponges live?==
Of the 9'000 or so species of sponges, only about 100 live in fresh water, the rest are marine.
{{co|Could you be more precise here. Where do they live, in which oceans, at which depth, etc... etc....}}
[
[Utilisateur:Pierre.brawand|Pierre.brawand]] 30 janvier 2011 à 15:08 (CET)
{
{co|You should explain HOW do Sponges feed themselves? Why are Sponges considered as ANIMALS despite the fact that they lack some characteristics of Animals...?}}
[[
Utilisateur:Pierre.brawand|Pierre.brawand]] 30 janvier 2011 à 15:09 (CET)

=What are Cnidarians?=
The name Cnidaria comes from the Greek word "cnidos" which means stinging nettle. Cnidarians (phylum Cnidaria) are mostly marine species (more than 10'000) and are the oldest of the true metazoan phyla . All the Cnidaria are aquatic and nearly all are marine. There are '''four groups''' of Cnidarians: '''Hydrozoa, Scyphozoan, Cubozoa, and Anthozoa'''. 

'''Hydrozoans''' are in general small and colonial animals that usually exist as polyps. They live attached to rocks, sea grasses, and other solid objects, where they feed on small crustaceans and other zooplankton. There are around 2,700 described species of hydrozoans: this species have a life cycle with both polyp and medusa stages. 

'''Scyphozoans''', or jellyfish, are found in the oceans of the world and eat small planktonic animals (zooplankton) and sometimes fish. There are about 200 described species of scyphozoans, and, like hydrozoans, they have three separate life stages: a sexually produced planula stage, a strictly asexual polyp stage (usually not colonial), and a dominant, sexual, medusa stage. They can measure between a few centimeters and a meter. 

'''Cubozoans''', or box jellyfish, are a class in which the medusa is the dominant life stage. They are small, rectangular boxes (1-10 cm in length) with four tentacles (nematocyst coverded tentacles or bundless of tentacles). There are about twenty species of Cubozoans. They are fast and agile swimmers and fish on fish and crustaceans. Unlike the other Cnidarians, Cubozoans have numerous well-developed eyes along the margin of the bell which are remarkably complex because they have a cellular cornea, a lens, pigment cells and a photoreceptive, enervated retina. This eyes are used for feeding and during reproduction. Their life cycle is simila to Scyphozoans with one exception: box jellies mate. Cubozoans are highly toxic and can kill humans. 

'''Anthozoans''' have te greatest species diversity, with over 6'000 species. They have too the greatest morphological diversity, encompassing sea anemones, sea pansies, sea whips and fans, corallimorphs and soft and hard corals. The dominant life stage og Anthozoa is the polyp. It shows a greater complexity than Hydrozoans and Scyphozoans polyps. Unlike the other Cnidarians, its gut is partially subdivided by thin, folded layers of tissue taht are vertically arranged around the inside og the gut. So its medusa is completely absent. Planula develop into a reproductively capable polyp and the development can occur within the gastrovascular cavity or in the external milieu.

==What are the main characteristics of Cnidarians?==
They are two different forms of Cnidarians body: '''Polypoid Shape''' or '''Medusoid Shape'''. 

'''The polypoid''' is the shape of corals and anemones. Its characteristics are the mouth and the tentacles facing up and the other side is anchored to a colony of the same aspect: for example, a coral reef. 
'''Medusoids''' are jellyfish. They are free swimmers and their tentacles and mouth are pointed down (the opposite of polypoids). 
Cnidarians have a mouth and a simple digestive system at the center of their tentacles, that is the reason why they are considered as animals and not plants. They have a radial symmetry. All cnidarians use tentacles which have stinging cells to subdue and capture food. They generally eat small planktonic animals.

 Cnidarians reproduce both '''asexually''' and '''sexually'''.
The reproduction is made by budding. That is a process of asexual reproduction in which a new individual develops from some generative anatomical point of the parent organism.

{{co|not enough description of the two forms of reproduction}}
[[U
tilisateur:Pierre.brawand|Pierre.brawand]] 30 janvier 2011 à 15:10 (CET)

 *see '''Appendix Cnidarians 1'''

==Where do Cnidarians live?==

They live under water. Some Cnidarians live in the oceans and seas, and a few live in freshwater. But they mostly live in saltwater or oceans.

{{co|OK... good start but you should now produce more information...}}
[
[U
tilisateur:Pierre.brawand|Pierre.brawand]]

----
back to [[Animals_2BIbDF09_10/11]] 
back to [[Accueil]]

Sponges Cnidarians 2BIbDF09 10/11

2011-01-31T09:12:37Z

MorganeV : /* What are the main characteristics of Sponges? */

=What are Sponges?=
Sponges, from the Latin pore bearers, are very primitive animals of the phylum Porifera, more precisely they are the first multicellular animals. They evolved very early from colonial protists. Their ancestors are the choanoflagellates (group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of the animals). There are between 8'000 and 9'000 species of sponges, depending of the textbook. They are '''invertebrates''', which are animals without backbones. There exist different sponges of different forms and different shapes, including tubes, fans, cups, cones, blobs, barrels, and crusts.

*see '''Appendix Sponges 1'''

==What are the main characteristics of Sponges?==
Sponges are loosely organized and lack true tissues. The body of a sponge has two outer layers separated by an acellular gel layer called the mesophyl (also called the mesenchyme). In the gel layer are either spicules (supportive needles made of calcium carbonate) or spongin fibers (a flexible skeletal material made from protein). Their sizes are from a few millimeters to more than 2 meters in diameter. They don't have any symmetry.

 The body of a sponge looks similar to a vase pierced with small holes and pores. It has thousands of pores. Water is drawn through the little pores into a central cavity, the spongocoel, then flows out the sponge through a larger opening, the osculum. In this process, they collect small particulate matter and tiny planktons, by the trapping action of the choanocytes, which are collar cells. That's why we call them filter feeders. Sponges do not have nervous, digestive or circulatory systems.

 As adults, sponges are sessile. That means that they are permanently attached to a substrate and are unable to move on their own. Most sponges are hermaphrodites (each adult can act as either the female or the male in reproduction). They produce sperm and eggs which are formed by aggregations of cells called amoebocytes in the body wall. During the proper time of the year, they release sperm cells into the sea. These cells are then captured using the same process the sponges use to capture food. The difference is that the sperm cells are moved to the "ova" of the sponge parent. And now the fertilization can take place. The eggs develop within the parent, the amount of time this takes depends on the species. When the eggs reach the "larvae" stage they are released back into the sea to seek out a place to settle and colonize.

Sponges can be either white, red, orange, green, yellow, brown, purple or black. They are known for regenerating from fragments that are broken off.. 

{{co|good. Maybe you could create an Appendix document showing the main characteristics of Sponges}}[
[Utilisateur:Pierre.brawand|Pierre.brawand]]

==Where do Sponges live?==
Of the 9'000 or so species of sponges, only about 100 live in fresh water, the rest are marine.
{{co|Could you be more precise here. Where do they live, in which oceans, at which depth, etc... etc....}}[
[Utilisateur:Pierre.brawand|Pierre.brawand]] 30 janvier 2011 à 15:08 (CET)
{
{co|You should explain HOW do Sponges feed themselves? Why are Sponges considered as ANIMALS despite the fact that they lack some characteristics of Animals...?}}
[[
Utilisateur:Pierre.brawand|Pierre.brawand]] 30 janvier 2011 à 15:09 (CET)

=What are Cnidarians?=
The name Cnidaria comes from the Greek word "cnidos" which means stinging nettle. Cnidarians (phylum Cnidaria) are mostly marine species (more than 10'000) and are the oldest of the true metazoan phyla . All the Cnidaria are aquatic and nearly all are marine. There are '''four groups''' of Cnidarians: '''Hydrozoa, Scyphozoan, Cubozoa, and Anthozoa'''. 

'''Hydrozoans''' are in general small and colonial animals that usually exist as polyps. They live attached to rocks, sea grasses, and other solid objects, where they feed on small crustaceans and other zooplankton. There are around 2,700 described species of hydrozoans: this species have a life cycle with both polyp and medusa stages. 

'''Scyphozoans''', or jellyfish, are found in the oceans of the world and eat small planktonic animals (zooplankton) and sometimes fish. There are about 200 described species of scyphozoans, and, like hydrozoans, they have three separate life stages: a sexually produced planula stage, a strictly asexual polyp stage (usually not colonial), and a dominant, sexual, medusa stage. They can measure between a few centimeters and a meter. 

'''Cubozoans''', or box jellyfish, are a class in which the medusa is the dominant life stage. They are small, rectangular boxes (1-10 cm in length) with four tentacles (nematocyst coverded tentacles or bundless of tentacles). There are about twenty species of Cubozoans. They are fast and agile swimmers and fish on fish and crustaceans. Unlike the other Cnidarians, Cubozoans have numerous well-developed eyes along the margin of the bell which are remarkably complex because they have a cellular cornea, a lens, pigment cells and a photoreceptive, enervated retina. This eyes are used for feeding and during reproduction. Their life cycle is simila to Scyphozoans with one exception: box jellies mate. Cubozoans are highly toxic and can kill humans. 

'''Anthozoans''' have te greatest species diversity, with over 6'000 species. They have too the greatest morphological diversity, encompassing sea anemones, sea pansies, sea whips and fans, corallimorphs and soft and hard corals. The dominant life stage og Anthozoa is the polyp. It shows a greater complexity than Hydrozoans and Scyphozoans polyps. Unlike the other Cnidarians, its gut is partially subdivided by thin, folded layers of tissue taht are vertically arranged around the inside og the gut. So its medusa is completely absent. Planula develop into a reproductively capable polyp and the development can occur within the gastrovascular cavity or in the external milieu.

==What are the main characteristics of Cnidarians?==
They are two different forms of Cnidarians body: '''Polypoid Shape''' or '''Medusoid Shape'''. 

'''The polypoid''' is the shape of corals and anemones. Its characteristics are the mouth and the tentacles facing up and the other side is anchored to a colony of the same aspect: for example, a coral reef. 
'''Medusoids''' are jellyfish. They are free swimmers and their tentacles and mouth are pointed down (the opposite of polypoids). 
Cnidarians have a mouth and a simple digestive system at the center of their tentacles, that is the reason why they are considered as animals and not plants. They have a radial symmetry. All cnidarians use tentacles which have stinging cells to subdue and capture food. They generally eat small planktonic animals.

 Cnidarians reproduce both '''asexually''' and '''sexually'''.
The reproduction is made by budding. That is a process of asexual reproduction in which a new individual develops from some generative anatomical point of the parent organism.

{{co|not enough description of the two forms of reproduction}}
[[U
tilisateur:Pierre.brawand|Pierre.brawand]] 30 janvier 2011 à 15:10 (CET)

 *see '''Appendix Cnidarians 1'''

==Where do Cnidarians live?==

They live under water. Some Cnidarians live in the oceans and seas, and a few live in freshwater. But they mostly live in saltwater or oceans.

{{co|OK... good start but you should now produce more information...}}
[
[U
tilisateur:Pierre.brawand|Pierre.brawand]]

----
back to [[Animals_2BIbDF09_10/11]] 
back to [[Accueil]]

Sponges Cnidarians 2BIbDF09 10/11

2011-01-17T10:02:38Z

MorganeV : /* What are the main characteristics of Sponges? */

Sponges Cnidarians 2BIbDF09 10/11

2011-01-17T09:31:42Z

MorganeV : /* What are Sponges? */

Sponges Cnidarians 2BIbDF09 10/11

2011-01-17T09:30:50Z

MorganeV : /* What are the main characteristics of Sponges? */

Sponges Cnidarians 2BIbDF09 10/11

2011-01-10T10:27:21Z

MorganeV : /* What are Sponges? */

Sponges Cnidarians 2BIbDF09 10/11

2011-01-10T09:59:03Z

MorganeV : /* What are Sponges? */

=What are Sponges?=
Sponges, from the Latin pore bearers, are very primitive animals of the phylum Porifera, more precisely they are the first multicellular animals.They evolved very early from colonial protists. There are between 8'000 and 9'000 species of sponges, depending of the textbook. Their ancestors are the choanoflagellates (group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of the animals).

*see '''Appendix Sponges 1'''

==What are the main characteristics of Sponges?==
They are loosely organized and lack true tissues. Their sizes are from a few millimeters to more than 2 meters in diameter.
The body of a sponge looks similar to a vase pierced with small holes and pores. Sponges do not have nervous, digestive or circulatory
systems.
==Where do Sponges live?==

=What are Cnidarians?=
Cnidarians (phylum Cnidaria) are mostly marine species (more than 10'000).

==What are the main characteristics of Cnidarians?==

==Where do Cnidarians live?==

Sponges Cnidarians 2BIbDF09 10/11

2011-01-10T09:57:22Z

MorganeV : /* What are the main characteristics of Sponges? */

=What are Sponges?=
Sponges, from the Latin pore bearers, are very primitive animals of the phylum Porifera, more precisely they are the first multicellular animals.They evolved very early from colonial protists. They are loosely organized and lack true tissues. There are between 8'000 and 9'000 species of sponges, depending of the textbook. Their sizes are from a few millimeters to more than 2 meters in diameter. The body of a sponge looks similar to a vase pierced with small holes and pores. Sponges do not have nervous, digestive or circulatory systems. Their ancestors are the choanoflagellates (group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of the animals).

*see '''Appendix Sponges 1'''

==What are the main characteristics of Sponges?==
The height of sponges is between 1 cm to 2 m. Sponges have no nerves or muscles but the individual cells can sense and react to changes in the environment. Sponges don't really have tissues, because the cells are relatively unspecialized.

==Where do Sponges live?==

=What are Cnidarians?=
Cnidarians (phylum Cnidaria) are mostly marine species (more than 10'000).

==What are the main characteristics of Cnidarians?==

==Where do Cnidarians live?==

Sponges Cnidarians 2BIbDF09 10/11

2010-12-06T10:25:08Z

MorganeV : /* What are Cnidarians? */

=What are Sponges?=
Sponges, from the Latin pore bearers, are very primitive animals of the phylum Porifera, more precisely they are the first multicellular animals.They evolved very early from colonial protists. They are loosely organized and lack true tissues. There are between 8'000 and 9'000 species of sponges, depending of the textbook. Their sizes are from a few millimeters to more than 2 meters in diameter. The body of a sponge looks similar to a vase pierced with small holes and pores. Sponges do not have nervous, digestive or circulatory systems. Their ancestors are the choanoflagellates (group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of the animals).

*see '''Appendix Sponges 1'''

==What are the main characteristics of Sponges?==

==Where do Sponges live?==

=What are Cnidarians?=
Cnidarians (phylum Cnidaria) are mostly marine species (more than 10'000).

==What are the main characteristics of Cnidarians?==

==Where do Cnidarians live?==

Sponges Cnidarians 2BIbDF09 10/11

2010-12-06T10:04:03Z

MorganeV : /* What are Sponges? */

=What are Sponges?=
Sponges, from the Latin pore bearers, are very primitive animals of the phylum Porifera, more precisely they are the first multicellular animals.They evolved very early from colonial protists. They are loosely organized and lack true tissues. There are between 8'000 and 9'000 species of sponges, depending of the textbook. Their sizes are from a few millimeters to more than 2 meters in diameter. The body of a sponge looks similar to a vase pierced with small holes and pores. Sponges do not have nervous, digestive or circulatory systems. Their ancestors are the choanoflagellates (group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of the animals).

*see '''Appendix Sponges 1'''

==What are the main characteristics of Sponges?==

==Where do Sponges live?==

=What are Cnidarians?=

==What are the main characteristics of Cnidarians?==

==Where do Cnidarians live?==

Sponges Cnidarians 2BIbDF09 10/11

2010-12-06T09:49:32Z

MorganeV : /* What are Sponges? */

=What are Sponges?=
Sponges, from the Latin pore bearers, are very primitive animals of the phylum Porifera, more precisely they are the first multicellular animals.They evolved very early from colonial protists. They are loosely organized and lack true tissues. There are between 8'000 and 9'000 species of sponges, depending of the textbook. Their sizes are from a few millimeters to more than 2 meters in diameter. The body of a sponge looks similar to a vase pierced with small holes and pores. Sponges do not have nervous, digestive or circulatory systems.

==What are the main characteristics of Sponges?==

==Where do Sponges live?==

=What are Cnidarians?=

==What are the main characteristics of Cnidarians?==

==Where do Cnidarians live?==

Consignes

2010-12-05T16:30:48Z

MorganeV : /* 2BIbDF09 BRAWAND */

== Rédaction d'une page Wiki ==

Le but principal est de rédiger une page sous la forme de questions-réponses.

*Chaque question se traduira sous la forme d'un titre: il faut donc veiller à utiliser des titres explicites
*Plus la question sera précise et plus la réponse sera courte et facile à donner. Il faut donc définir les bonnes questions!
*Hiérarchiser les titres: posez-vous d'abord telle question, puis telle autre, etc.
*La réponse à une question va souvent vous servir de base pour une nouvelle question... et le cycle continue!
*Indiquez systématiquement la source de vos informations: URL, source bibliographique, etc.
*Variez vos sources en puisant dans les différents supports à disposition: livres, revues, articles, internet, etc.
*Tenez compte de ce qui a déjà été écrit sur le Wiki: ce n'est pas la peine de répéter inutilement des informations: une lecture préalable de la page s'imposera donc pour savoir où vous en êtes!
*Attention à l'orthographe et la syntaxe... ce que vous écrivez doit être lisible par tous!
*Datez et signez vos contributions à l'aide de: <nowiki>~~~~ (4 tildes)</nowiki>= [[Utilisateur:Pierre.brawand|Pierre.brawand]] 27 août 2006 à 21:29 (MEST)

== Correction des pages Wiki ==
Vos pages seront corrigées régulièrement de la manière suivante! La ''couleur verte italique '' indiquera une correction de vos '''enseignants exclusivement'''.

Exemple:
 
L'Homme descend du Singe et le Singe descend de l'arbre...
 

{{co|Tout porte à croire que l'Homme descende du Singe et que donc, tous deux, aient un ancêtre commun relativement proche...}}

A vous de tenir compte des corrections en reformulant vos propos afin d'améliorer votre document!

Veuillez dans ce cas enlever le code de formatage de {{co|couleur verte italique}} utilisé par vos enseignants.

== Statut du document ==
*Le document lui-même n'est pas important, c'est ce qui a pu être construit à l'intérieur des élèves par toutes les étapes de l'activité qui est important. (F. Lombard)

*En d'autres termes... c'est le travail que vous produirez ensemble dans la mise sur pied du document qui vous sera utile à la compréhension du sujet.
*Ne perdez donc pas de temps à "formater" vos pages inutilement...

==Traitement des images==

Pour des raisons évidentes et légales, il n'est pas possible de charger nos pages Wiki avec des images.
Pourtant celles-ci sont particulièrement utiles à la bonne compréhension de certains mécanismes biologiques complexes...

Vous pouvez sans problème contourner ce problème de la manière suivante:

*dans la page Wiki, indiquez le lien de l'image si celle-ci a été prise sur Internet: ce lien permettra d'accéder à l'image "en ligne".
*copiez l'image sur le dossier Doc_annexes.doc qui se trouve sur le serveur Mimosa et renommer le fichier en indiquant le numéro de cours suivi du numéro de l'annexe:
::Exemple: '''4BIOS01_Annexe3.doc'''
*Complétez sur le document les points suivants:
:*le numéro de l'annexe
:*le titre de l'image
:*votre prénom
:*la source
:*un commentaire (légende explicative, etc.)
*Ce fichier word, sera ensuite imprimé et rajouter sous forme d'annexe au futur polycopié.
[[Utilisateur:Pierre.brawand|Pierre.brawand]] 25 septembre 2006 à 23:06 (MEST)

== Présentations orales ==
*Répartissez-vous le temps de parole entre les différents membres du groupe
*Partagez-vous les différentes parties de la présentation
*Indiquez le titre de votre présentation et son contexte (quel chapitre, ou quelle partie de chapitre, etc.)
*Exposez au préalable le plan de votre présentation: qui va parler de quoi et pourquoi!
*Description des résultats: projetez tout d'abord la page Wiki puis peut-être illustrez vos propos à l'aide d'une figure (en indiquant les sources)
*Exposez l'état de vos recherches: à l'heure actuelle de nos recherches, nous en sommes là... mais la semaine prochaine nous en serons peut-être là... Surtout, ne pas fermer les portes... il est normal que vous ne maitrisiez pas tout le sujet dès le début.
*Pour les présentations finales (qui seront généralement évaluées), prévoyez un support multimédia de type présentation Power Point avec au maximum 10 diapos. Prévoyez une diapositive d'introduction ainsi qu'une pour la conclusion.
*Faites des liens si possible avec les présentations des autres groupes
*Conclusions: la partie la plus intéressante! Elle doit permettre de soulever des questions chez vos auditeurs!
*Réponses aux questions: écoutez bien les questions... et réfléchissez quelques secondes avant de répondre. Soyez le plus clair possible dans votre réponse. Au besoin, répétez vos propos.
 
:''Site intéressant donnant des conseils pour l'élaboration du présentation orale scientifique.''
:*http://www.ipmc.cnrs.fr/~duprat/techcom/oral.htm#debut

==Elaboration des posters==
:''Quelques sites intéressants donnant des conseils pour l'élaboration des posters.''
:*http://www.ipmc.cnrs.fr/~duprat/techcom/poster.htm#conseil
:*http://mdc2007.fpms.ac.be/documents/posters.pdf
:*http://www4.utc.fr/~sp01/Fiches%20Pratiques/Consignes%20Poster.pdf

== Evaluation ==

L'évaluation portera sur différents aspects:

*Participation à la création des pages
*Connaissances acquises = tests de connaissances
*Aptitudes à transposer vos connaissances dans un situation particulière = tests d'aptitudes

*Présentations orales en classe:
**Plan de la présentation
**Clarté, concision, précision
**Vulgarisation
**Résultats
**Questions soulevées (débat)

==Rapports de laboratoire==

Quelques conseils pour l'écriture de vos rapports de biologie...
Suivez le plan suivant en indiquant les différentes rubriques

*'''Titre:'''
**Donner un titre général au laboratoire

*'''Introduction:'''
**Décrire le but de l'expérience ou de l'observation.
::*expérimentation: décrire le problème posé et résumer les travaux ou les connaissances précédents.
::*observations: décrire l'objet qui va être observé et ajouter quelques notes (provenance, mode de vie, etc…)

*'''Matériel et Méthodes:'''
**Technique utilisée
**Matériel nécessaire ou à disposition: liste précise des équipements, origine, lieu d'observation, date, météo, etc…
**Dessins et plans si nécessaire.

*'''Résultats:'''
**Penser à introduire vos résultats et à les exposer.
**Sous forme de tableaux, graphiques, dessins, avec légende ou texte explicatif.
**Vos résultats doivent être statistiquement valables… donc comparez-les à ceux de vos camarades de classe ou répéter l'expérience suffisamment de fois!
**Ne rien discuter ni commenter dans cette rubrique. Il s'agit ici uniquement de présenter les résultats.

*'''Discussion:'''
**Relier les résultats obtenus au but initial de l'expérience ou de l'observation.
**Interpréter les résultats en les reliant aux connaissances actuelles.
**Définir et proposer un éventuel modèle qui pourrait expliquer les résultats obtenus.

*'''Conclusion:'''
**Proposer d'autres expériences à faire afin de poursuivre l'étude de manière plus complète.
**Placer le travail dans un contexte plus large, discuter des conséquences, des implications, etc…
**La Conclusion peut être liée directement avec la partie Discussion sous forme de Discussion/Conclusion.

*'''Remarques:'''
**rendre un rapport propre, clair
**soigner la présentation: rapport dactylographié, entête comprenant: nom prénom, groupe, date
**résultats explicitement présentés
**textes des légendes écrits droits et reliés au dessin par un trait tiré à la règle
**dessins clairs et précis, suffisamment grands, en utilisant un bon crayon

 [[Utilisateur:Pierre.brawand|Pierre.brawand]] 19 septembre 2008 à 21:59 (MEST)

== Signatures ==
*Datez et signez vos contributions à l'aide de: <nowiki>~~~~ (4 tildes)</nowiki> que vous placerez après "lu et approuvé:"
*Ecrivez <nowiki> </nowiki> en fin de ligne pour faire un saut de ligne simple

====2BIOS01 BRAWAND====
lu et approuvé: [[Utilisateur:Pierre.brawand|Pierre.brawand]] 4 octobre 2010 à 16:09 (CEST) 
lu et approuvé: [[Utilisateur:EstelaC|EstelaC]] 5 octobre 2010 à 18:24 (CEST) 
lu et approuvé: [[Utilisateur:CoralineB|CoralineB]] 6 octobre 2010 à 11:09 (CEST) 
lu et approuvé: [[Utilisateur:MarcM|MarcM]] 6 octobre 2010 à 16:04 (CEST) 
lu et approuvé: [[Utilisateur:KouroshC|KouroshC]] 6 octobre 2010 à 20:14 (CEST) 
lu et approuvé:[[Utilisateur:DaniaER|DaniaER]] 6 octobre 2010 à 22:11 (CEST) 
lu et approuvé: [[Utilisateur:MarionS|MarionS]] 6 octobre 2010 à 23:22 (CEST) 
lu et approuvé: [[Utilisateur:JonathanW|JonathanW]] 7 octobre 2010 à 11:00 (CEST) 
lu et approuvé: [[Utilisateur:DanielaI|DanielaI]] 2 décembre 2010 à 11:46 (CET) 
lu et approuvé: [[Utilisateur:AmelR|AmelR]] 2 décembre 2010 à 11:48 (CET) 
lu et approuvé: 
lu et approuvé: 
lu et approuvé: 
lu et approuvé: 
lu et approuvé: 

====2BIbDF09 BRAWAND====
lu et approuvé: [[Utilisateur:Pierre.brawand|Pierre.brawand]] 29 novembre 2010 à 11:26 (CET) 
lu et approuvé: [[Utilisateur:CecileM|CecileM]] 29 novembre 2010 à 11:31 (CET) 
lu et approuvé: [[Utilisateur:AgnesP|AgnesP]] 29 novembre 2010 à 19:06 (CET) 
lu et approuvé: [[Utilisateur:DavinaZ|DavinaZ]] 4 décembre 2010 à 13:17 (CET) 
lu et approuvé: [[Utilisateur:NathalieR|NathalieR]] 4 décembre 2010 à 20:39 (CET) 
lu et approuvé: [[Utilisateur:AlizeeC|AlizeeC]] 5 décembre 2010 à 12:05 (CET) 
lu et approuvé: [[Utilisateur:GaranceV|GaranceV]] 5 décembre 2010 à 12:26 (CET) 
lu et approuvé: [[Utilisateur:OceaneG|OceaneG]] 5 décembre 2010 à 16:35 (CET) 
lu et approuvé: [[Utilisateur:MelanieD|MelanieD]] 5 décembre 2010 à 17:16 (CET) 
lu et approuvé: [[Utilisateur:MorganeV|MorganeV]] 5 décembre 2010 à 17:30 (CET) 
----
retour à [[Accueil]]